Python support

Add python-xunit-parser.ts with associated case statement
Add python-xunit to reporter docs in action.yml
Add tests
Update README

Resolves #244
Resolves #633

src/parsers/python-xunit/python-xunit-parser.ts

@@ -0,0 +1,8 @@
+import {ParseOptions} from '../../test-parser'
+import {JavaJunitParser} from '../java-junit/java-junit-parser'
+
+export class PythonXunitParser extends JavaJunitParser {
+  constructor(readonly options: ParseOptions) {
+    super(options)
+  }
+}