added working obsidian workspace with basic documentation

[bamtests]

Tested as both a standalone application and in an Ubuntu desktop image. Feel free to pull the images I have built to test/try it out: kasmweb-obsidian and ubuntu-jammy-dind-rootless-obsidian

To properly finalize, if accepted, I assume someone would want to fill out the rest of the demo.txt file with the proper information, but I tried to add what I could otherwise.

I figured others would also want to use Obsidian in their workspaces, so I wanted to share.

[sfcampbell]

@bamtests I love the Obsidian commit you PR'd!

I have a nascent idea for "GitHub Dev" Kasm image that I haven't started working on yet, but the gist is: I want to build a Kasm image with Code/VSCode and Obsidian in a single image with persistant or symlinked storage to maintain GitHub credentials, local Git repos, and Code/VSCode plugins. The goal is for devs who would like to switch between workstations, without complications of premature commits and unnecessarily frequent pulls; a dev could move from workstation-to-workstation seamlessly... Would you be interested in teaming up on a project like that?

If so DM me!