Add configurations for:
* Prettier (https://prettier.io)
* markdownlint (https://github.com/DavidAnson/markdownlint)
* Black formatter (https://black.rtfd.io)
* cspell (https://www.npmjs.com/package/cspell)
* Conda environment. Just run:
    conda env create
  to set up the whole developer environment
* VIM (.lvimrc skeleton only)
* VSCode (.vscode)

Also adds more files to gitignore