Support `content_for ""` first argument completion

[charlespwd]

We want "block" or "blocks" completion in the LiquidString node.

{% content_for "█"%}
{% content_for "b█" %}

Steps:

• Create a ContentForCompletionProvider in theme-language-server-common/src/completions/providers
• Import it and add an instance to the list of providers in theme-language-server-common/src/completions/CompletionProvider
• Logic should be something like
  • Early return if the node from params.completionContext is not of type NodeTypes.String and the parentNode isn't a ContentForMarkup (check out the RenderSnippetCompletionProvider for inspiration)
  • Return completion items for block or blocks

[Smintfy]

Hello, @charlespwd

I added "block" and "blocks" completion inside the content_for tag. I hope the attached video is the desired feature or output. Hope you can check it out :)

I had to use the branch feature/content_for_tag to be able to use the NodeTypes.ContentForMarkup because I couldn't find it on the main branch 😅

https://github.com/user-attachments/assets/9f5aec3d-f6ed-467b-906e-c35f73856bc8

[charlespwd]

That's exactly what we want :o

Also, #568 is merged on main if you want to make a PR :) :pray:

[charlespwd]

Fixed by #577 and #582. Thank you @Smintfy :pray: