Fixing plugin-github.mustache so it executes correctly (#379)

Author: andrewshell

templates/plugin-github.mustache

@@ -1,3 +1,4 @@
+{{=<% %>=}}
 name: Testing
 
 on:
@@ -31,6 +32,9 @@ jobs:
           php-version: ${{ matrix.php-version }}
           tools: phpunit-polyfills:1.1
 
+      - name: Install SVN
+        run: sudo apt-get update && sudo apt-get install -y subversion
+
       - name: Setup tests
         run: bash bin/install-wp-tests.sh wordpress_tests root root 127.0.0.1 latest true