Running "bundle exec jekyll serve" freezes on "Requiring: jekyll-postcss"

Platform: Windows

I'm trying to get TailwindCSS working with my new Jekyll project, and when I run `bundle exec jekyll serve --verbose` it freezes. Force-quitting the process with ctrl+c displays the following:

```
$ bundle exec jekyll serve --verbose
Logging at level: debug
Jekyll Version: 4.2.2
Configuration file: xxxxxxxxx/_config.yml
Logging at level: debug
Jekyll Version: 4.2.2
Requiring: jekyll-feed
Requiring: jekyll-postcss
------------------------------------------------
Jekyll 4.2.2 Please append `--trace` to the `serve` command
for any additional information or backtrace.
------------------------------------------------
Traceback (most recent call last):
29: from C:/Ruby27-x64/bin/jekyll:23:in `'
28: from C:/Ruby27-x64/bin/jekyll:23:in `load'
27: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/exe/jekyll:15:in `'
26: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/mercenary-0.4.0/lib/mercenary.rb:21:in `program'
25: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/mercenary-0.4.0/lib/mercenary/program.rb:44:in `go'
24: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/mercenary-0.4.0/lib/mercenary/command.rb:221:in `execute'
23: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/mercenary-0.4.0/lib/mercenary/command.rb:221:in `each'
22: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/mercenary-0.4.0/lib/mercenary/command.rb:221:in `block in execute'
21: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/lib/jekyll/commands/serve.rb:86:in `block (2 levels) in init_with_program'
20: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/lib/jekyll/command.rb:91:in `process_with_graceful_fail'
19: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/lib/jekyll/command.rb:91:in `each'
18: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/lib/jekyll/command.rb:91:in `block in process_with_graceful_fail'
17: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/lib/jekyll/commands/build.rb:30:in `process'
16: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/lib/jekyll/commands/build.rb:30:in `new'
15: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/lib/jekyll/site.rb:36:in `initialize'
14: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/lib/jekyll/site.rb:133:in `setup'
13: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/lib/jekyll/site.rb:319:in `instantiate_subclasses'
12: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/lib/jekyll/site.rb:319:in `tap'
11: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/lib/jekyll/site.rb:321:in `block in instantiate_subclasses'
10: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/lib/jekyll/site.rb:321:in `map!'
9: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/lib/jekyll/site.rb:321:in `block (2 levels) in instantiate_subclasses'
8: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-4.2.2/lib/jekyll/site.rb:321:in `new'
7: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-postcss-0.5.0/lib/jekyll/converters/postcss.rb:16:in `initialize'
6: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-postcss-0.5.0/lib/jekyll/converters/postcss.rb:16:in `fetch'
5: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-postcss-0.5.0/lib/jekyll/converters/postcss.rb:16:in `block in initialize'
4: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-postcss-0.5.0/lib/jekyll/converters/postcss.rb:16:in `new'
3: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-postcss-0.5.0/lib/jekyll-postcss/socket.rb:13:in `initialize'
2: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-postcss-0.5.0/lib/jekyll-postcss/socket.rb:62:in `start_dev_server'
1: from C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-postcss-0.5.0/lib/jekyll-postcss/socket.rb:62:in `open'
C:/Ruby27-x64/lib/ruby/gems/2.7.0/gems/jekyll-postcss-0.5.0/lib/jekyll-postcss/socket.rb:62:in `initialize': Interrupt
```

Here are all of my current config files, with what I believe are irrelevant lines stripped out:

**_config.yml**:
```yaml
# Build settings
plugins:
- jekyll-feed
- jekyll-postcss

# example from https://github.com/stefcoetzee/jekyll-tailwind/blob/main/_config.yml
sass:
sourcemap: never

# disable caching for Tailwind JIT
postcss:
cache: false

# files Jekyll should not delete from .site
keep_files:
- css/tailwind.css
- css/tailwind.css.map
```

**postcss.config.js**
```js
module.exports = {
plugins: [
require('postcss-import'),
require('tailwindcss'),
require('autoprefixer'),
...(process.env.JEKYLL_ENV == "production"
? [require('cssnano')({ preset: 'default' })]
: [])
]
};
```

**tailwind.config.js**
```js
module.exports = {
content: [
'./_includes/**/*.html',
'./_layouts/**/*.html',
'./_posts/*.md',
'./*.html',
],
theme: {
extend: {}
},
variants: {},
plugins: [
require('@tailwindcss/typography'),
],
}
```

I'm happy to include any other details that you might need.

Start with lib/jekyll-postcss/socket.rb, especially start_dev_server, and reproduce the Windows command `bundle exec jekyll serve --verbose` using the reported _config.yml and PostCSS configuration. Trace why startup remains blocked at the socket initialization; done means Jekyll serves successfully without freezing while retaining the reported Tailwind CSS setup.

Written by the indexing model from the issue text.