Allow uploading block-based themes

[aristath]

Right now uploading a block-based theme in the .org repository is blocked by the theme-check that runs on upload. Authors are forced to add hacks and useless code in their themes to bypass some of these checks. However, themes are not allowed to contain unused code so the process currently followed is this:

• Author uploads a theme that passes theme-check
• Author contacts the themes-team reps.
• The team reps do a preliminary review of the theme, and set the theme to be a special-case theme. This allows theme updates to bypass theme-check when uploaded
• Author uploads their "real" theme.

The above process is unsustainable and if someone tries to upload a valid FSE theme the upload will fail. It's OK right now since block-based themes are still experimental, but we have started getting requests and questions about how theme-authors can upload their themes, so we're expecting more submissions to start coming in soon.

Suggestions: Either theme-check should be disabled for block-based themes, OR some checks should be skipped - see ​https://github.com/WordPress/theme-check/pull/280

[williampatton]

For this ticket we need to update the Theme Check plugin. First we have to define a definite way to identify FSE themes and use that to determine which checks to perform in the plugin.

[dd32]

Just noting this Theme Check PR to adapt it to allow FSE themes to pass ​https://github.com/WordPress/theme-check/pull/280

[poena]

The Theme Check updates are ready for testing.

Summary of the checks that are skipped
for block themes and why:
​https://github.com/WordPress/theme-check/issues/279#issuecomment-851774058

[dd32]

As of today & [11035], the new Theme Check is deployed on WordPress.org.

I think that should fix this ticket?