feat(gha): Auto-publish releases

- GHA release workflow is updated to use an action for uploading all assets. The
	action docs say it updates a release if one already exists, and since this
	triggers on release and we pass a release tag we know the release already
	exists.
- GHA release candidate workflow is updated to auto-publish a pre-release
	release on push to a `release/**` branch. A script is added and used to
	generate a release message made up of the commits since the last release of
	any kind.
- ACT profiles are added to allow locally testing these workflows without
	needing to push and wait for GHA to run.
- Docs are updated to note how to test the workflows locally.

.github/act/release-candidate-push.json

@@ -0,0 +1,6 @@
+{
+  "ref": "refs/heads/release/1.2",
+  "repository": {
+    "full_name": "jgoguen/crosspoint-reader"
+  }
+}

.github/act/release-published.json

@@ -0,0 +1,9 @@
+{
+  "action": "published",
+  "release": {
+    "tag_name": "1.38"
+  },
+  "repository": {
+    "full_name": "jgoguen/crosspoint-reader"
+  }
+}