docs: Update contributing docs

[edgarrmondragon]

• Include pre-commit installation instructions.
• Document use of tox environments to automate development tasks.

Closes #741

New Documentation: https://meltano-sdk--745.org.readthedocs.build/en/745/CONTRIBUTING.html

[codecov]

Codecov Report

Merging #745 (e60e154) into main (44b48c8) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #745   +/-   ##
=======================================
  Coverage   85.35%   85.35%           
=======================================
  Files          34       34           
  Lines        3408     3408           
=======================================
  Hits         2909     2909           
  Misses        499      499           

---

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 44b48c8...e60e154. Read the comment docs.