build: Overhaul build & deployment workflow (#3267)

* Fixes #3250

* build: Overhaul build & deployment workflow

- Move to release drafter
- Replace publishing with gradle nexus
- Conventional commits are handy
- Determine build status in gh actions before deploying

.github/release-drafter.yml

@@ -0,0 +1,20 @@
+categories:
+  - title: '🐛 Fixes'
+    label: 'Bugfix'
+  - title: '✨ Features'
+    label: 'Feature'
+  - title: '🧭 Changes'
+    label: 'Enhancement'
+  - title: '📦 Dependency updates'
+    labels:
+      - 'Renovate'
+      - 'Dependency updates'
+change-template: '- $TITLE @$AUTHOR (#$NUMBER)'
+change-title-escapes: '\<*_&@'
+exclude-contributors:
+  - 'renovate'
+  - 'renovate-bot'
+template: |
+  ## PlotSquared v6.
+
+  $CHANGES