Rails default architectures are not all supported by this gem

Out of the box, `rails new` with Rails 8.0.2.1 produces a _Gemfile.lock_ with the following platforms:

```
PLATFORMS
aarch64-linux
aarch64-linux-gnu
aarch64-linux-musl
arm-linux-gnu
arm-linux-musl
x86_64-linux
x86_64-linux-gnu
x86_64-linux-musl
```

Following the installation instructions, which only mention adding _sqlean_ to the _Gemfile_, you end up with something like the following on `bundle install`:

```
> bundle install
Fetching gem metadata from https://rubygems.org/.........
Could not find gems matching 'sqlean' valid for all resolution platforms (arm-linux-gnu, arm-linux-musl, arm64-darwin-24, x86_64-linux, x86_64-linux-gnu, x86_64-linux-musl) in rubygems repository https://rubygems.org/ or installed locally.

The source contains the following gems matching 'sqlean':
* sqlean-0.1.0-aarch64-linux
* sqlean-0.1.0-arm64-darwin
* sqlean-0.1.0-x64-mingw
* sqlean-0.1.0-x86_64-darwin
* sqlean-0.1.0-x86_64-linux
* sqlean-0.2.0-aarch64-linux-gnu
* sqlean-0.2.0-arm64-darwin
* sqlean-0.2.0-x64-mingw
* sqlean-0.2.0-x86_64-darwin
* sqlean-0.2.0-x86_64-linux-gnu
* sqlean-0.2.0-x86_64-linux-musl
* sqlean-0.3.0-aarch64-linux-gnu
* sqlean-0.3.0-arm64-darwin
* sqlean-0.3.0-x64-mingw
* sqlean-0.3.0-x86_64-darwin
* sqlean-0.3.0-x86_64-linux-gnu
* sqlean-0.3.0-x86_64-linux-musl
```

The README does have a section about supported platform and includes the following note:

```
If you need support for one of these platforms, please open an issue.
```

I don't need these other platforms per se. But, I thought I'd raise this as a friction point for anyone looking to use _sqlean_ with a new Rails application. I tried with various versions of Rails, CRuby, and Bundler. I'm not sure what code is responsible for populating all of the platforms. But, it's occurring with the latest Rails (8.0.2.1), CRuby (3.4.5), and Bundler (2.7.1) as of 2025-09-02.

Since the missing platforms aren't supported upstream, the only real solution is to document a mitigation. I got things working by removing the following platforms:

* `arm-linux-gnu`
* `arm-linux-musl`

I'm not really sure why `bundle install` worked with `aarch64-linux-musl` in the `PLATFORMS` list.