docs: add installation steps for release

[justlevine]

What

This PR documents the installation steps for the v0.1.0 release on GH + Composer

How

Cherry picked from #42 and altered to reflect the latest trunk after #35

[Copilot]

Pull Request Overview

This PR adds comprehensive installation documentation for the Abilities API v0.1.0, providing multiple installation methods for different use cases. The documentation has been updated to reflect the latest state after recent changes and includes practical examples for plugin authors.

• Replaces basic git clone instructions with multiple installation options
• Adds dependency management guidance for plugin developers
• Includes code examples for checking API availability and version requirements

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_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.43%. Comparing base (f55439d) to head (382aac0).
⚠️ Report is 1 commits behind head on trunk.

Additional details and impacted files

@@            Coverage Diff            @@
##              trunk      #48   +/-   ##
=========================================
  Coverage     88.43%   88.43%           
  Complexity       94       94           
=========================================
  Files             8        8           
  Lines           519      519           
=========================================
  Hits            459      459           
  Misses           60       60           

Flag	Coverage Δ
unit	88.43% <ø> (ø)

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[jonathanbossenger]

Added a few suggestions, but nothing that's really blocking a merge. We can always tweak things as we go.

[jonathanbossenger]

I assume we will have a release available soon, because right now this is not available.

[justlevine]

Yup, I believe this is the last PR before we cut v0.1.0

[jonathanbossenger]

One note on these checks, if the code that's doing the checking is inside of a plugin that loads after wp-abilities-api (eg wp-my-plugin) then this might not work. It's on the lower end of the scale of the realm of possibility, but still possible enough to warrant a note about it. I experienced this recently when setting up my workshop examples after recent updates to the mcp-adapter.