Resolve markdownlint Issues

# 🐛 Summary #
Revert .mdl_config.yaml changes made in PR #5 and fix all issues flagged by pre-commit.
To run pre-commit locally, run `pre-commit markdownlint --all-files`

To setup pre-commit, run `./setup-env`.
If it fails to run, follow the instructions returned in the console. This includes installing pyenv pyenv-virtualenv, and adding its path to .zhrc.

To run the check-case-conflict hook, run `pre-commit run check-case-conflict --all-files`.
To run a different hook, replace `check-case-conflict` with the name of the hook. The list of available hooks is in .pre-commit-config.yaml