[SR-15317] [Swift-DocC] Emit a warning for a "See Also" task group within a Topics section.

[ethan-kusters]

Previous ID	SR-15317
Radar	rdar://60684559
Original Reporter	@ethan-kusters
Type	Bug
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	0
Component/s	Swift-DocC
Labels	Bug, DiagnosticsQol, StarterBug
Assignee	@Kyle-Ye
Priority	Medium

md5: 963ca050244e96619e8c563b137ddc6e

Issue Description:

It's easy to accidentally write a "See Also" section as part of a Topics section (like the following) instead of as it's own second-level heading like DocC expects:

# ``ModuleName/SymbolName``

Symbol overview.

## Topics

### First Task Group

- ``ChildSymbol``

### See Also

- ``RelatedSymbol``

However, DocC requires See Also sections to be written as second-level headings beneath a Topics section, not as subsections of Topics sections. DocC should emit a warning with a fixit upon encountering this. In this case, the fixit would update the example to the following:

# ``ModuleName/SymbolName``

Symbol overview.

## Topics

### First Task Group

- ``ChildSymbol``

## See Also

- ``RelatedSymbol``