Create a contributor's guide for the ILDH

[greatislander]

Is your feature request related to a problem?

The ILDH will need a document to help people contribute content or edits to the Handbook. Topics may include:

• Using git
• Using markdown syntax
• Submitting a pull request
• Style guide

Describe the solution you'd like

Not applicable.

Describe alternative solutions you've considered

Not applicable.

Additional context or notes

Migrated from ILDH-5.

[BlueSlug]

I've prepared some instructions for contributing to the ILDH which were specifically tailored to one of our contributors, and I feel these would be a good solution to this issue. This may not make it into the next release (v1.2.0 at time of writing), but it should be fairly straightforward to adapt the instructions to be more general and less point-form and to include some links to Markdown cheat-sheets and the like.

@greatislander if you'd like to talk about this at any point, feel free to reach out! Otherwise I'll plan to proceed with that work when I have some spare cycles :)