Make a zip-version

### Enhancement Summary
Many projects provides a zip version that does not need installing.
If at all possible(?), i suggest we make that feature.

#### Justification
It is a nice and feel-safe way to install software, and is a well known way for many packs (VLC, IrfanView, amo), and could encourage users to try out new versions, because a roll-back is drag and drop of either a zip'-content, or the backed-upped previous folder' content

Start by reviewing how LMMS currently packages and distributes releases across its supported platforms. Define the required contents, installation behavior, rollback expectations, and release workflow for a portable zip before implementation; the issue names no files, tests, or entry points.

Written by the indexing model from the issue text.