Add stable identifiers to Obsidian publish page sections

Use case or problem

We can create a publish.js file to customize our Obsidian Publish Websites. From there, to customize certain parts of the page, we need to find the right DOM elements. Currently, since those don’t have an id, we have to find those by className, which is not ideal

Proposed solution

Add the id property to stable elements of Obsidian publish Websites.

Current workaround (optional)

Use document.getElementsByClassName('...')[0], which is not great from a DX point of view