Overleaf Support (LaTeX Editor)

**What problem does this solve?**
Overleaf is one of, if not the most, used LaTeX editor platforms. However, currently, Harper does not work on Overleaf documents, even though #56 added generic LaTeX support. Currently Harper acts as if it wasn't enabled when I have the document open, even though the plugin claims it's enabled (see picture below). Sometime after #1395 was posted, Harper stopped checking Overleaf documents (not sure if this is a coincidence or not). This fixed the bug #1395 raised but rendered Harper unable to be of use to me as Overleaf is where I primarily write.

**Proposed Solution**
If Overleaf is domain enabled by the user, when a document is opened, Harper should parse the document and provide suggestions, pursuant to the LaTeX support merged in #56.

**Examples**

**Component**
- [ ] Core engine
- [x] Plugin/Extension
- [ ] Other: _____

**Additional Context**
Harper parses other websites without issue (e.g. GitHub and Ars Technica). I have tested Harper with Overleaf on the following browsers without success:
- Firefox
- Zen
- LibreWolf
- Ungoogled Chromium
- Brave
- Helium (pictured above)

Start by tracing the plugin/extension path that handles domain enablement and document opening, then compare its behavior with the generic LaTeX support added in #56 and the regression discussed in #1395. Reproduce the failure on an Overleaf document in one of the listed browsers; done means enabled Overleaf documents receive Harper suggestions without breaking other websites.

Written by the indexing model from the issue text.