docs: swap dead RTD link for GitHub docs URL (closes #58)

[bluetoothbot]

What

Replace the broken uart-devices.readthedocs.io link/badge with a link to the rendered docs/ directory on GitHub.

Why

https://uart-devices.readthedocs.io/ returns "Project not found" (issue #58) because the project has never been imported on Read the Docs. The in-repo RTD config (.readthedocs.yml, docs/conf.py, pyproject.toml docs group) is correct — the gap is an admin-side import on app.readthedocs.org.

Until RTD is wired up, this PR keeps the documentation link clickable instead of pointing at a 404.

How

• README: removed the readthedocs.svg build-status badge and pointed the Documentation line at github.com/bluetooth-devices/uart-devices/tree/main/docs.
• pyproject.toml: same swap for the [tool.poetry] documentation = … URL (this flows into PyPI's "Documentation" project link).
• .readthedocs.yml and docs/conf.py left untouched — once the project is imported on RTD, the badge + URLs can be reverted in a one-line follow-up.

Testing

• git diff --stat: 2 files changed, 2 insertions, 5 deletions.
• No code paths touched; no tests required.

Alternative

If you'd rather import the project on RTD now (https://app.readthedocs.org → Import a Project → bluetooth-devices/uart-devices), this PR can be closed instead — the existing config should build on first try.

Closes #58.

---

Quality Report

Changes: 2 files changed, 2 insertions(+), 5 deletions(-)

Code scan: clean

Tests: passed (2 passed)

Branch hygiene: clean

Generated by Kōan post-mission quality pipeline

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.68%. Comparing base (c90d926) to head (a411017).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #75   +/-   ##
=======================================
  Coverage   73.68%   73.68%           
=======================================
  Files           1        1           
  Lines          38       38           
  Branches        3        3           
=======================================
  Hits           28       28           
  Misses         10       10           

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