Add phpstan and Resolve issues

[bhavz-10]

Description

Setup phpstan for the theme.

Technical Details

Adding phpstan setup along with the baseline setup so that errors that are to be ignored can be added and setup a baseline again.

Checklist

Screenshots

To-do

Fixes/Covers issue

Fixes #634

[Adi-ty]

The issue mentions that level 5 is the target and that any pre-existing issues should be handled via a baseline rather than lowering the level. Moving to level 8 feels like a fairly meaningful step up in strictness, so I wanted to check whether that was intentional. If it was, could we call that out explicitly and get sign-off on the tighter standard? Otherwise, it may make sense to keep this at level 5 for now and rely on the baseline as described in the issue.

[Adi-ty]

array<string, static> works here, but the key type could be a bit more precise and the value type is slightly broader in practice because the cache can hold instances for multiple classes. Consider array<class-string, object> for the cache and narrowing the looked-up entry to static at return time with /** @var static $singleton */ before the return.

[bhavz-10]

This is right 🙌
I added the fix for this and pushed it in the PR

[Adi-ty]

A small stub file wired via bootstrapFiles resolves it cleanly and lets us drop the baseline entry. Happy to leave it for now if you prefer to keep the change small.

[bhavz-10]

Added a boostrap file and removed the errors from baseline file and left it empty.

[bhavz-10]

The issue mentions that level 5 is the target and that any pre-existing issues should be handled via a baseline rather than lowering the level. Moving to level 8 feels like a fairly meaningful step up in strictness, so I wanted to check whether that was intentional. If it was, could we call that out explicitly and get sign-off on the tighter standard? Otherwise, it may make sense to keep this at level 5 for now and rely on the baseline as described in the issue.

Hello @aryanjasala

Why we should take a stricter approach:

• Adjustability: We can always reduce the strictness later if it causes a nuisance.
• Customization: Users can still use the baseline for their own custom setups.
• Visibility: Rather than decreasing the level to hide issues, we will maintain a baseline with documented errors. This ensures they are tracked and can be resolved at a later point.

[Adi-ty]

$block parameter is typed as array<mixed> across all three methods, which allows integer keys, but the parsed block array always uses string keys (blockName, attrs etc.). array<string, mixed> would be a more accurate type here.