Package README styling

[simurai]

This PR improves the styling of package READMEs

• <table> styling
• <kbd> styling
• more fixes like a, hr, blockquote, pre

Fixes #620

[simurai]

Empty cells in <table> don't get rendered. Maybe that shouldn't be a blocker for this PR?

[jlord]

Interesting that it doesn't render empty cells. Not so terrible if empty cells are on the end, but if they're in the middle then it could throw off the table. I found the issue for this in marked.

@gjtorikian we use your roaster for our markdown. Have you run into the problem with empty table cells being skipped by marked before? I think we could patch it by handling empty cells in the table cell block level render methods in marked. What do you think? If it's not a terrible idea I can get the PR started.

[gjtorikian]

I think that makes sense.

If the PR doesn't get merged we might also be able to getting away with some kind of hack using   to insert a space.

[jlord]

@simurai Turns out that the settings-view readme doesn't have empty cells, but the raw markdown just didn't provide the any cells at all beyond the first two columns. github.com fills these in apparently.

So at first, once I discovered that, I was like, cool, there's actually no problem. But then I realized, once I gave it the empty cells, it didn't render the last cell unless it had content.

I used the marked render wrapper to insert content into blank cells, even tried the   and that didn't help either, the last empty cell never gets included. Hmmm...

[izuzak]

@jlord I think that's this issue: atom/markdown-preview#206

[jlord]

@izuzak ah, ok, thanks ✨

Then I think we should 🚢 this PR @simurai for the table styles 👍