Either convert .rst files to markdown, or add an rst linting script to CI

[AlexWaygood]

Silly rst markup errors aren't being caught by the CI (e.g. #72 fixes a bunch that look like they've been there for a while).

We should probably either convert these files to markdown, or add linting script like CPython's rstlint.py to the CI.

Files that need to be ported are:

• README.rst: Port the README to markdown #152
• CHANGELOG.rst: Port CHANGELOG.rst to markdown #153
• CONTRIBUTING.rst: Port CONTRIBUTING.rst to markdown #154

[Akuli]

I think we should just use markdown, because we are more familiar with its syntax and won't make silly errors.

[AlexWaygood]

I think we should just use markdown, because we are more familiar with its syntax and won't make silly errors.

I agree.

[KotlinIsland]

I fixed a bunch more in #117, I'm completely unfamiliar with rst but the support in PyCharm (syntax highlighting and preview window) made it extremely easy to work with.

[AlexWaygood]

I fixed a bunch more in #117, I'm completely unfamiliar with rst but the support in PyCharm (syntax highlighting and preview window) made it extremely easy to work with.

Thank you very much!