Ability to set explicit "named" anchors for headings

[alexakreizinger]

Request

Add the ability to explicitly define anchors for headings.

Current behavior

Anchors always match the name of the associated heading. For example, ## this is my heading generates the anchor example.com/page#this-is-my-heading.

Reason for request

There are times where I need to use two headings with the same name on the same page. Currently, Mintlify appends -2, -3, etc. to anchors for headings with identical names, but being able to set custom anchor names is more predictable behavior and makes it easier to link between pages/headings without issue.

Example implementation

In other markdown-based docs tools I've used, the syntax has been something like this:

## this-is-my-heading [#custom-anchor]

...which generates the anchor example.com/page#custom-anchor.