rework the build system

- use rustls for reqwest, so we don't need to compile OpenSSL
- use better defaults for build arguments in Dockerfile
- add Continuous Integration workflow for master branch and it's pull requests
- add Release workflow for tags matching SemVer
- add release template for automatic release notes generation with GH CLI
- remove old and unused assets under .github

.github/release.yml

@@ -0,0 +1,17 @@
+changelog:
+  exclude:
+    labels:
+      - ignore-for-release
+  categories:
+    - title: Breaking Changes 🛠
+      labels:
+        - breaking-change
+    - title: New Features 🎉
+      labels:
+        - enhancement
+    - title: Bug fixes 🐛
+      labels:
+        - bug
+    - title: Other Changes 🔄
+      labels:
+        - "*"