[WIP][2.x] Add template annotations

[WyriHaximus]

FYI just filed https://github.com/reactphp/promise/pull/227 and https://github.com/reactphp/promise/pull/228

Both are a getting support out there and then improve on it kind of PR.

[zmitic]

Sorry for barging but I am really interested in this PR and would like to remove my own stubs. Should I wait for merge or use PR branch instead?

[WyriHaximus]

@zmitic Honestly same, will have a look at this again during the weekend and hopefully, this got resolved in recent PHPStan updates. But currently support for mixed scalar and scalar through PromiseInterface is blocking this

[WyriHaximus]

Opened https://github.com/phpstan/phpstan/issues/8707 to hopefully get the last few functions fully in

[WyriHaximus]

PR's to address our current template param buggy use can be found here:

• https://github.com/reactphp/dns/pull/212
• https://github.com/reactphp/promise-timer/pull/63
• https://github.com/reactphp/promise-stream/pull/35
• https://github.com/reactphp/http/pull/487