Add coverage report

[nickmoreton]

Add Codecov

This adds codecov to display coverage test results using the example:
https://github.com/codecov/example-python

Ticket URL: https://projects.torchbox.com/projects/wordpress-to-wagtail-importer-package/tickets/94

• Testing
  • CI passes
  • These changes do not reduce test coverage
• Documentation.
  • This PR adds or updates documentation

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (main@e930c8f). Click here to learn what that means.
The diff coverage is n/a.

❗ Current head f1b288c differs from pull request most recent head 8aca4ea. Consider uploading reports for the commit 8aca4ea to get more accurate results

@@           Coverage Diff           @@
##             main     #105   +/-   ##
=======================================
  Coverage        ?   64.93%           
=======================================
  Files           ?       32           
  Lines           ?     1249           
  Branches        ?      224           
=======================================
  Hits            ?      811           
  Misses          ?      395           
  Partials        ?       43           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e930c8f...8aca4ea. Read the comment docs.

[nimasmi]

My name is Nick Smith, and I approve these changes.

[nickmoreton]

Thanks Nick