Headings not available in block type select dropdown when using `createHeadingBlockSpec`

[simonjnesta]

Describe the bug Usually, when highlighting text in a paragraph block, you are able to change the block type to a heading. When using custom heading config using createHeadingBlockSpec, the option to convert to a heading disappears.

To Reproduce Expected behaviour:

• Open basic BlockNote example: https://www.blocknotejs.org/examples/basic/minimal
• Enter some text and highlight it
• Open the block type dropdown
• Headings are present

Broken behaviour:

• Open configuring default blocks example: https://www.blocknotejs.org/examples/custom-schema/configuring-blocks
• Highlight some text
• Open the block type dropdown
• Headings are not present

Misc

Minimal example: https://stackblitz.com/edit/github-xbcndn1l?file=src%2FApp.tsx

It seems that in the dropdown:

• The headings all disappear if you specify allowToggleHeadings: true
• The headings will not be filtered if levels: [1, 2, 3] is specified (i.e. you can convert to heading 6)