tip: prepare for merging into pyTooling/Actions

tip/README.md

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+**tip** is a Docker GitHub Action written in Python.
+
+**tip** allows to keep a GitHub Release of type pre-release and its artifacts up to date with latest builds. Combined with a workflow that is executed periodically, **tip** allows to provide a fixed release name for users willing to use daily/nightly artifacts of a project.
+
+Furthermore, when any [semver](https://semver.org) compilant tagged commit is pushed, **tip** can create a release and upload assets.
+
+# Usage
+
+The following block shows a minimal YAML workflow file:
+
+```yml
+name: 'workflow'
+
+on:
+  schedule:
+    - cron: '0 0 * * 5'
+
+jobs:
+  mwe:
+    runs-on: ubuntu-latest
+    steps:
+
+    # Clone repository
+    - uses: actions/checkout@v2
+
+    # Build your application, tool, artifacts, etc.
+    - name: Build
+      run: |
+        echo "Build some tool and generate some artifacts" > artifact.txt
+
+    # Update tag and pre-release
+    # - Update (force-push) tag to the commit that is used in the workflow.
+    # - Upload artifacts defined by the user.
+    - uses: eine/tip@master
+      with:
+        token: ${{ secrets.GITHUB_TOKEN }}
+        files: |
+          artifact.txt
+          README.md
+```
+
+# Options
+
+All options can be optionally provided as environment variables: `INPUT_TOKEN`, `INPUT_FILES`, `INPUT_TAG`, `INPUT_RM` and/or `INPUT_SNAPSHOTS`.
+
+## token (required)
+
+Token to make authenticated API calls; can be passed in using `{{ secrets.GITHUB_TOKEN }}`.
+
+## files (required)
+
+Either a single filename/pattern or a multi-line list can be provided. All the artifacts are uploaded regardless of the hierarchy.
+
+For creating/updating a release without uploading assets, set `files: none`.
+
+## tag
+
+The default tag name for the tip/nightly pre-release is `tip`, but it can be optionally overriden through option `tag`.
+
+## rm
+
+Set option `rm` to `true` for systematically removing previous artifacts (e.g. old versions). Otherwise (by default), all previours artifacts are preserved or overwritten.
+
+## snapshots
+
+Whether to create releases from any tag or to treat some as snapshots. By default, all the tags with non-empty `prerelease` field (see [semver.org: Is there a suggested regular expression (RegEx) to check a SemVer string?](https://semver.org/#is-there-a-suggested-regular-expression-regex-to-check-a-semver-string)) are considered snapshots; neither a release is created nor assets are uploaded.