CI: Update GHA configuration to also run on the main branch (#158)

* CI: Update GHA configuration to also run on the `main` branch

This is intended to toggle the badge on the Build Status page [1] into
green.

[1] https://cratedb.com/docs/crate/clients-tools/en/latest/status.html

* CI: Optimize GHA configuration about redundant concurrent jobs

* README: Improve document title

.github/workflows/main.yml

@@ -2,7 +2,14 @@
 name: Main
 
 on:
-  - pull_request
+  push:
+    branches: [ main ]
+  pull_request: ~
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 
 jobs:
   lint:

README.md

@@ -1,4 +1,4 @@
-# crate-airflow-tutorial
+# CrateDB Airflow Tutorial
 Orchestration Project - Astronomer/Airflow tutorials