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/scripts/package-artifacts.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+set -euo pipefail
+
+export OUTPUT_DIR
+mkdir -p "$OUTPUT_DIR"
+
+printenv CARGO_BUILD_TARGETS | awk -F, '{
+  for (i = 1; i <= NF; i++)
+    if (match($i, /^([^-]+)(-[^-]+)*-(linux|windows|darwin)(-[^-]+)*$/, matches))
+      printf "%s\0%s\0%s\0", $i, matches[3], matches[1]
+    else print "DEBUG: awk: No regex match for field index " i ": \047" $i "\047" > /dev/stderr
+}' | xargs -0 -n 3 "$(dirname -- "$(readlink -f -- "$0")")/compress-artifact.sh"