textbundle support

### 🚀 The feature, motivation and pitch

A common problem with markdown files is when you link to attachments (images, etc) there's not a common place to put them. This means that markdown files with links to attachments are intrinsically not portable between apps.

Textbundle (https://textbundle.org/) attempts to solve that by introducing a new file type which is just a directory that includes the markdown file and assets folder internally.

e.g. structure like this:
```
neovim bug.textbundle
├── assets
│   ├── Screenshot 2024-06-12 at 3.26.20 PM.png
│   └── Screenshot 2024-06-13 at 9.57.18 PM.png
├── info.json
└── text.md
```

This is really neat since it would mean linking to assets can be portable between applications. And in particular syncing a directory of notes that have linked to assets across devices works out of the box with applications that support textbundle.

Since the markdown files are just nested in one additional folder layer, in general textbundle should already work (ish) with obsidian.nvim.

--

What would first-class support in obsidian.nvim look like?
1. Being able to link to notes by referencing the text bundle name (e.g. a wikilink of `[[neovim bug]]` should work, and accessing it should show the markdown file)
2. Making it easy to add assets to a text bundle (e.g. by copying a file to the assets directory from the clipboard or otherwise, and then setting autocompleting the appropriate path)

--

Currently the smoothest notetaking app I've seen that supports text bundles is https://fsnot.es/ It's worthwhile to clone/build/test that app: https://github.com/glushchenko/fsnotes

### Alternatives

This came about because I'm looking for a robust and polished app to access my notes on ios. Unfortunately the obsidian app is too buggy for daily use for me. I only use obsidian.nvim on desktop.

Currently the best thing I've found for ios is iaWriter, however attachments and inline images are broken because the path it expects images to be at is not portable between obsidian.nvim and iaWriter.

I haven't found any other markdown app that isn't buggy on mobile.

Alternatively I've only found proprietary format notes apps like apple notes and notion to even have a potentially useful experience on mobile. Currently I'm taking some notes in the apple notes app with the intention of copying them over later.

### Additional context

_No response_

The issue names no files or tests. Start by reviewing obsidian.nvim's current wikilink and asset-handling behavior, then compare the textbundle structure and fsnotes implementation; done means textbundle note links resolve correctly and assets can be added with portable paths.

Written by the indexing model from the issue text.