Typography updates

Re: issue #105

David tweeted me pointing me in the direction of John’s tweet asking for some help with the typography tweaks. I can’t turn down Pomf — so here is a PR with some updates. I’ve not done anything too mental / majorly different, however have made a fair few marginal gains with the reading experience.

I also tidied up some of the css in line with the code standards.

# Changes

## Typography tweaks

- headings more clearly related to content with better spacing (gestalt theory of grouping FTW)
- line-height tweaked at each breakpoint 
- text-rendering: optimizeLegiblity; removed (not great to use this bad boy)
- font-feature-settings used instead
- ::selection color + text-shadow removed (known issue of going mental with OpenType features - works with just background-color)
- change spacing between type elements to just use margin-bottom (to make it easier to control)
- implemented modular scale for post type sizing for each breakpoint
- hang lists at larger breakpoints
- use correct numbered values for font-weight


## Large screen breakpoint added

- desktop breakpoint takes styles from previous base styles
- base css now for 1600px+ viewports
- improves reading experience on large screens


## CSS formatting consistency

- always using double quotes
- consistent spacing after colons
- uppercase # colour values
- border colour always first