The idea is to make it very easy for anyone to add or update a project entry. All you need to do is to submit a PR with the project details; feel free to start with the template, and you can also add images (thumbnail and/or a main picture for the project page) to the images subfolder (just use the same relative URL that is in the template). Any kind of project using Matrix is welcome; if you are unsure which category to use, just use "other".
Jekyll requires a date in the project filename; we use the date to sort the various project lists (newest projects first). It might be best to submit new entries with a date like 2015-01-01.
Any questions or comments? Come talk to us in #matrix:matrix.org!