Move children schema to strands remove use of deprecated module

[cortadocodes]

Contents (#112)

Operations

• Add ReadTheDocs config file
• Fix codecov upload
• Use reusable workflows
• Test with python3.9 too
• Upgrade actions

Dependencies

• Fix documentation requirements

Refactoring

• Move children and manifest schemas to Strands

Fixes

• Fix accordion usage in docs
• Swap deprecated/removed pkg_resources for importlib

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 87.78%. Comparing base (30ce2cf) to head (78a71c6). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #112 +/- ## ========================================== + Coverage 87.54% 87.78% +0.23% ========================================== Files 7 7 Lines 257 262 +5 ========================================== + Hits 225 230 +5 Misses 32 32 ```

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