[FEATURE]: a feature about table of contents for source code mode

[yu2chuan]

Is your feature request related to a problem? Please describe.

If table of contents also works for souce code mode, it should be easier for users to find where they want to edit.

Describe the solution you'd like

The table of contents can funtion not only in the Wysiwyg but also in the source code mode

Describe alternatives you've considered

Additional context

[drl990114]

This part may be optimized in later versions and is more complicated.