To allow svg caching add the version to the svg file and sed the used
version file in the css file.

Remove the unrequired -2 option when attaching a tmux session. Get rid
of the warning when selecting the window by providing the missing + and
remove the unrequired split-window.

The icons are part of the free Octicons set

Append the git tag version to the JS/CSS files so we can set cache
headers in nginx.

Closes: #2

Reduce the size of the svg on build with ~ 50% by using svgcleaner.

Show the increase of website size in merge requests.

As a bonus terser supports ES6.

Instead of relying on made up pixel values, use bulm'a definitions
except for > 2048px as that's where bulma is at the moment lacking in
mixin presets.