Add a Custom Block for Katex (fixes #741)

[Excellencedev]

/claim #741
/fixes #741

Description:

Custom Block for KaTeX Equations (#741)

This PR adds a new custom block for rendering LaTeX equations using KaTeX, addressing the feature request in #741. The block provides a user-friendly interface for inputting and editing mathematical expressions directly in the editor, similar to Notion's equation feature.

Changes

• New Block Implementation: Added packages/core/src/blocks/Equation/block.ts defining the equation block spec.

  • Config: Stores LaTeX code in props.latex.
  • Content: "none" (no inline content, as LaTeX is prop-based).
  • Parse: Detects <div class="equation" data-latex="..."> from HTML.
  • Render: Editable div for LaTeX input with live KaTeX preview below. Updates on input.
  • toExternalHTML: Renders KaTeX HTML with data-latex attribute for serialization.

• Integration:

  • Exported from packages/core/src/blocks/index.ts.
  • Added to defaultBlockSpecs in packages/core/src/blocks/defaultBlocks.ts for default schema inclusion.
  • Imported in defaultBlocks.ts from the Equation block file.

• Dependencies: Added katex to @blocknote/core dependencies for rendering.

• Keyboard Shortcut: Cmd/Ctrl + Alt + E to insert a new equation block at the cursor position.

• TypeScript Fixes: Adjusted spec structure using createBlockSpec with proper overloads to resolve type errors.

Usage

• Insert via shortcut or slash menu (if extended).
• Edit the LaTeX code in the input field; the preview updates live.
• Invalid LaTeX shows "Invalid LaTeX" in red.
• Exports to HTML with rendered KaTeX for static documents.

[vercel]

@Excellencedev is attempting to deploy a commit to the TypeCell Team on Vercel.

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[Excellencedev]

Please review this PR and drop a comment so that I know what I need to do

[Excellencedev]

Please approve the workflow and try to review this PR (it fixes #741) @nperez0111 @YousefED
And please drop a comment so I know what you think. Thank you

[nperez0111]

I don't think we are going to accept this PR @Excellencedev, there were other attempts before you, and none were satisfactory. I made my own version a few weeks ago & even it was not satisfactory: #1987

We are likely going to move in a different direction with this. I'm unsure how this works, maybe you should take down the bounty @YousefED ?