Fix CSS errors

[nlhkabu]

Fix the following CSS errors (mostly a result of the CSS restructure):

• Reduce the font size of the badges

• Remove underline on sidebar links (also make cursor pointer)

• Make the introduction text align left

• Make the button group share internal borders

• Make the package history design work with just one release (remove vertical line)

• Add padding to the horizontal links

• Make the package card bg white

• Add padding to the bottom of the footer

• Fix alignment and spacing of Changelog title and button
  

[alexwlchan]

I think I have fixes for most of these; I’ll put up a PR when I’ve got a working dev environment and can check my changes are behaving as I expect. :)

[nlhkabu]

Hi @alexwlchan thanks for this. Actually, I already have fixes ready for all of these (I just have not integrated them yet), so it's probably not the best use of your time. Sorry, I should have been more explicit in the issue listing and assigned it to myself.