[v3] Alpha 1 release

[crazywhalecc]

I'm about to merge the v3-dev branch into v3, which will prompt us to release an alpha1 version first. Then we need to focus on infrastructure work:

• Documentation for migrating from v2
• Toolchain and build testing GHA for v3
• Switch static-php.dev to the v3 version, locking the v2 version (highlight the v2 link on the homepage)
• Migrate the repository to static-php/static-php (or not for now)
• Summarize the issues that need to be resolved before the alpha2 release