actions: Add tests to test some of the examples match the schema

[odscjames]

#57

[odscjames]

This only tests 2 JSON files - the rest I think are either meant to be broken or are only fragments so are harder to test. Let's get this in then look?

The main work here is generating a fake schema object to pass to the test code so that we test the schema in the repo and NOT the latest version online.

You can check this is working by editing the schema and running tests:

• changing network "name" to something else and seeing an additional field error come up
• changing network "name" type to "string" and seeing a JSON schema error come up

The Python checks don't actually use anything directly from the JSON schema files.

[lgs85]

Looks good and all appears to be working correctly.