chore: misc (#100) (this makes 2.0.0)

Co-authored-by: grialion <48643945+grialion@users.noreply.github.com>

- Fix license ambiguity (#88)
  - just the only/or-later ambiguity point, not adding SPDX identifyiers unless more people request it
- Better document kmscon (#91)
- Make 2.0.0 already to close #86
- Add a changelog
- Add packagers info (acutally just add them to install guide)
- Add AUR service packages (I'll take care of systemd and dinit, let others package the rest and leave systemd open for someone who actually uses it in docs)
- Make sure all makefile installs to `/usr/local` by default
- Simplify Makefile complexity by several orders

CHANGELOG.md

@@ -0,0 +1,10 @@
+<!-- Unspecified dates shall be in CET/CEST -->
+
+<!-- Add only very relevant changes, bottom to top -->
+<!-- By "very relevant" I mean big features or something manual packagers should know, like leftover files -->
+<!-- Once a release would be opened, group the last bunch of dangling changes, add release version as header and its date -->
+
+- Most stuff (most of `/etc` being a notable exception) now installs to `/usr/local` by default, check [`docs/PACKAGERS.md`](./docs/PACKAGERS.md).
+- Added a changelog.
+- Finally add proper (experimental) xorg support.
+- Systemd service install path changed to `/usr/local/lib/systemd`, there could be a leftover file at `/etc/systemd/system/lidm.service`.