workflow improvement + README.md update

[borntohonk]

overlaps with #6

[borntohonk]

for demo of the workflow see:
https://github.com/borntohonk/sys-patch/releases/tag/v1.5.4

uploading a "zip" to artifact will make it zipped a second time.

feeding artifacts a folder such as /out, will make it zip it only once.

[borntohonk]

How to control builds and releases:
change version number here https://github.com/impeeza/sys-patch/blob/master/Makefile#L5 as there cannot be duplicate tags, or duplicate named artifacts.

also with workflow_dispatch: you can manually start workflows on the workflow page.

[borntohonk]

after messy attempts, https://github.com/borntohonk/sys-patch/actions/runs/11589499731
there's now a conditional check for the tag to not publish a release if the tag already exists, and instead only creates an artifact