[inbox] Improvements to content presentation

@rufuspollock is already working on this.

Since Apr 15, 2022.

Context: we are using a remark-based pipeline for converting markdown => html (all inside of a nextjs react app).

We are also tending to use obsidian to edit the content in the wiki (though you can use any markdown editor you like!).

## Writing / Markdown

* [x] #99
* [x] Display videos nicely #88
* [x] Support proper obsidian wiki link syntaxes - #96
* [ ] Citation rendering #91 ie. `[@bernanke_essays_2004]` work see eg. https://web3.lifeitself.us/concepts/gold-standard
* [ ] Support additional obsidian markdown e.g.
* [ ] GFM: table and task list, footnotes (?)
```
| Markdown **table** |
**- [x] Task list**
```
* [ ] `#Tags`
* [ ] `$$LaTeX math$$`

## Big

* [ ] #127
* [ ] #128
* [x] #82
* [ ] #129

## Minor nice to have

* [x] Force email not empty on front page form
* [x] #130
* [x] 🔼 Navbar
* [x] ⏫ YouTube life itself channel link with icon
* [x] also in footer
* [x] Github repo link with icon
* [x] Life Itself icon (linking to lifeitself.us/labs)
* [x] Footer
* [x] YouTube icon and link - https://www.youtube.com/channel/UCmBq3VO9w_MLTKD_CHsYN-Q
* [x] Podcast icon and link to https://anchor.fm/life-itself
* [ ] #124

WONTFIX

* [x] 🔽 link to good first issue stuff from contribute section **WONTFIX. People who know what they are doing will work this out (?)**