Beaker: Add support for rendering PDFs with PDF.js

[pfrazee]

We're not going to support OS-native plugins, so Flash and Adobe's PDF viewer are out, but PDFs are pretty nice so maybe PDF.js can be used.

[webdesserts]

Heads up, I'm going to start looking into this.

[webdesserts]

@pfrazee Right now it looks like .md files are only formatted over the dat:// and http:// protocols. However they are not formatted over the file:// protocol. Is this intended, or should markdown and pdf files display a "viewer" over the file:// protocol as well?

[pfrazee]

@webdesserts what makes you say file:// isnt supported by markdown rendering?

[webdesserts]

@pfrazee Here was when I encountered the issue: https://clips.twitch.tv/SpineyBreakableYakinikuYouWHY?tt_medium=creation

You can see I drag and dropped a file into 0.8 and it was rendered raw.

[pfrazee]

Ah! Well that's a bug. Give me a few moments, I'll see if I can diagnose it.

[pfrazee]

Ok fixed. The issue was that the file:// protocol doesn't give a mimetype

[webdesserts]

@pfrazee ahh, Ok. Thanks! I'll keep this in mind when I work on the pdf detection.

[pfrazee]

Cool. Here's how I fixed it: https://github.com/beakerbrowser/beaker/commit/284e3361ac0749ce8a72a1f1e513b3c8e8a6ef39