- contains multiple small cosmetic fixes
- switch to the nord colour theme for css

Nord colour theme: https://www.nordtheme.com/docs/colors-and-palettes

This introduces necessary work for ticket support to the Smederee. =)
The idea is as follows:

1. Per repository you can create labels, milestones and tickets.
2. A ticket can be linked with multiple labels and/or milestones.
3. A ticket can be assigned to multiple accounts (assignees).

Several things are hard wired (e.g. ticket status) to reduce code
complexity.

This is all still incomplete but it compiles and does not interfere with
existing functionality. It also includes a dependency update.

This removes the fontawesome package and adds a template helper named `icon`
which creates icons on demand based upon the feather svg collection.
Thus we reduce the size of assets to be downloaded and eleminate a
dependency on JavaScript.