* replace all `var` declarations and use `const` where appropriate
* strip unnecessary temporary variables
* replace single character variable names
* replace multiline variable declarations
* simplify expressions
* replace invalid uses of parseInt

This updates the build toolchain to Vue CLI v5 and Tailwind 3.x along
with some other changes in tooling.

@tailwindcss/ui seems to be unused and has a peer dependency on
tailwind^1.0 that has been silently ignored.

- Add Gitlab pipeline with release stage
- Add docker build and push job
- Add create release job

Develop

See merge request !8