Merge rust-bitcoin/rust-bitcoin#2050: CI: add an automated github releases on new tags

c34c709681 CI: add an automated github releases on new tags (Einherjar)

Pull request description:

  Creates a `gh-release.yml` that runs on every new tag using the [`ncipollo/release-action`](https://github.com/ncipollo/release-action), which is one of the recommended actions after [GitHub's official `actions/create-release`](https://github.com/actions/create-release) was archived.

  The idea is to just have a release with the source code, no binary (although if wanted I can add that as well).
  A little bit of context: tcharding told me yesterday at TABConf that he copied manually all commits titles to the release notes somewhere (I think in crates.io?).
  This is an easy way to do it, just copy from the GitHub release.
  Finally, it is also positive to generate Releases from Tags since this increases the exposure of the repo (GitHub is highly social) while also signaling maturity.

  Here's an [example](https://github.com/oven-sh/bun/releases/tag/bun-v0.8.1) that I've found in a non-related repo that has the same `generateReleaseNotes: true` as this PR proposes

  <img width="857" alt="image" src="https://github.com/realeinherjar/rust-bitcoin/assets/136860407/41789514-8abf-4f58-b7ca-d2c352346923">

ACKs for top commit:
  apoelstra:
    ACK c34c709681
  tcharding:
    ACK c34c709681

Tree-SHA512: 06bc0276b5aca95e19965eadb79d0a4cf8606b222dce37f095247196fcac023458c34e35cf34fa2344bc274063e642b93b05dc796a27179567052c58ac4bc27a

.github/workflows/gh-release.yml

@@ -0,0 +1,15 @@
+name: GitHub Release
+
+on:
+  push:
+    tags:
+    - '*'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - uses: ncipollo/release-action@v1
+      with:
+        generateReleaseNotes: true