added selfhosted workflow ex and notes update

Author: sumanthgitty

.github/workflows/runner-selfhosted.yml

@@ -0,0 +1,17 @@
+# If you don't create a self-hosted runner you will see:
+# Waiting for a runner to pick up this job...
+name: Self-hosted Runner Workflow
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  example-job:
+    runs-on: self-hosted
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v3
+      - name: Run a one-line script
+        run: echo "Hello from a self-hosted runner!"

Learning-notes/Readme.md

@@ -291,3 +291,20 @@ runs-on: self-hosted
 
 If you specify an array of strings or variables, your workflow will execute on any runner that matches all of the specified runs-on values.
 
+#### Self-Hosted Runner
+Self-hosted runners can be:
+
+- Physical
+- Virtual
+- In a container
+- On-premises
+- In a cloud
+
+You can add self-hosted runners at various levels in the management hierarchy:
+
+- Repository-level runners are dedicated to a single repository.
+- Organization-level runners can process jobs for multiple repositories in an organization.
+- Enterprise-level runners can be assigned to multiple organizations in an enterprise account.
+
+To set up self-hosted, you need to add a runner and install the **GitHub Actions Runner** to connect the external compute to the self-hosted runner.
+After installing the GitHub Actions Runner, ensure **port 443** is open in your outbound rules to allow secure communication between the runner and GitHub.