feat(richtext-lexical): add new paragraph button below the editor

[AlessioGr]

Fixes #10448. If the last node in an editor was a block, the only way to add a paragraph below that block was to click the "+" button on the left hand-side of the editor.

This was not apparent enough for most users - thus this PR adds a more prominent, accessible "+" button that appear when hovering close to the end of the editor. This should make it easier to insert additional paragraphs, no matter what the last node is.

See it in action

CleanShot.2025-01-12.at.18.37.48.mp4

[rilrom]

This looks great. An edge case I can think of is whether there would be any overlap between the table add row button and this button.

[AlessioGr]

This looks great. An edge case I can think of is whether there would be any overlap between the table add row button and this button.

There's a tiny overlap - not sure if this edge case is worth extra complexity to fix it:

CleanShot.2025-01-12.at.19.09.21.mp4

We might also want to consolidate the styling of the table + button

[rilrom]

Looks good to me, still very much useable. Thanks for checking!

[AlessioGr]

CleanShot.2025-01-12.at.19.27.18.mp4

Made the styles for table buttons & add paragraph buttons more consistent

[tylandavis]

We should place the cursor on the new line, same as the + button on the left margin.

done

[github-actions]

🚀 This is included in version v3.17.0