[github] support ubuntu-20.04 runner (#1090)

* support ubuntu 20 runner

* test all runners

Author: ngraef

src/schemas/json/github-workflow.json

@@ -878,6 +878,7 @@
                     "self-hosted",
                     "ubuntu-16.04",
                     "ubuntu-18.04",
+                    "ubuntu-20.04",
                     "ubuntu-latest",
                     "windows-latest",
                     "windows-2019"

src/test/github-workflow/runs-on.json

@@ -0,0 +1,85 @@
+{
+  "name": "Test runs-on",
+  "on": [
+    "push"
+  ],
+  "jobs": {
+    "ubuntu": {
+      "runs-on": "ubuntu-latest",
+      "steps": [
+        {
+          "run": "echo 'Hello from ${{ runner.os }}'"
+        }
+      ]
+    },
+    "ubuntu-20": {
+      "runs-on": "ubuntu-20.04",
+      "steps": [
+        {
+          "run": "echo 'Hello from ${{ runner.os }}'"
+        }
+      ]
+    },
+    "ubuntu-18": {
+      "runs-on": "ubuntu-18.04",
+      "steps": [
+        {
+          "run": "echo 'Hello from ${{ runner.os }}'"
+        }
+      ]
+    },
+    "ubuntu-16": {
+      "runs-on": "ubuntu-16.04",
+      "steps": [
+        {
+          "run": "echo 'Hello from ${{ runner.os }}'"
+        }
+      ]
+    },
+    "macos": {
+      "runs-on": "macos-latest",
+      "steps": [
+        {
+          "run": "echo 'Hello from ${{ runner.os }}'"
+        }
+      ]
+    },
+    "macos-catalina": {
+      "runs-on": "macos-10.15",
+      "steps": [
+        {
+          "run": "echo 'Hello from ${{ runner.os }}'"
+        }
+      ]
+    },
+    "windows": {
+      "runs-on": "windows-latest",
+      "steps": [
+        {
+          "run": "echo 'Hello from ${{ runner.os }}'"
+        }
+      ]
+    },
+    "windows-2019": {
+      "runs-on": "windows-2019",
+      "steps": [
+        {
+          "run": "echo 'Hello from ${{ runner.os }}'"
+        }
+      ]
+    },
+    "matrix": {
+      "runs-on": "${{ matrix.os }}",
+      "strategy": {
+        "matrix": {
+          "os": ["ubuntu-20.04", "ubuntu-18.04", "ubuntu-16.04"]
+        }
+      },
+      "steps": [
+        {
+          "run": "echo 'Hello from ${{ runner.os }}'"
+        }
+      ]
+    }
+  }
+}