chore: add CODEOWNERS.md and README.md to apm-python team

[erikayasuda]

These two .md files should be approvable by anyone in apm-python, not just core.

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[github-actions]

CODEOWNERS have been resolved as:

.github/CODEOWNERS                                                      @DataDog/python-guild @DataDog/apm-core-python

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: erikayasuda/release-notes-codeowner
Commit report: 9a5bf6c
Test service: dd-trace-py

❌ 1 Failed (0 Known Flaky), 124798 Passed, 52096 Skipped, 4h 13m 32.88s Total duration (5h 22m 23.55s time saved)

❌ Failed Tests (1)

• test_propagation_memory_check[taintsource1-taintsource20] - test_iast_mem_check.py - Details

  Expand for error

   assert 28 == 27
    +  where 27 = num_objects_tainted()