CI examples

Hi there!

Not really an issue but as our project is being migrated to use wireit, I started wondering if we could use wireit within Azure Pipelines in a similar fashion to what is already provided for Github actions.

This seems simple enough by using one of the pre defined tasks for caching as is [well documented here](https://learn.microsoft.com/en-us/azure/devops/pipelines/release/caching?view=azure-devops), it would look something like this:

```
# Cache wireit
- task: Cache@2
inputs:
key: '"wireit" | "$(Agent.OS)"'
restoreKeys: |
wireit | "$(Agent.OS)"
wireit
path: $(wireit_cache)
displayName: Cache wireit

...

# Validate build
- script: |
pnpm install
WIREIT_CACHE=local pnpm run build
displayName: 'pnpm install and build'
```

Most of the functionality seems to 'just work', i need to figure out some azure specific quirks but that's something I'm happy to look at.

are you open for new PRs that present a couple of examples for implementing wireit in CI? I have something that would work for Azure, which could be great start for people interested in using wireit to speed up their CI, might be nice to set-up an examples folder

Thanks for your input! Happy to spend the time on a PR that gets an example in if you are open to the idea.