v0.2.13

Changes:
* how sources work have changed, such that they are loaded from a `sources.toml`
file. I would like to add a frontend for adding, editing and removing
several of these eventually, especially different types (such as those
not from GitHub).
* timerfiles now keep track of what source they belong to under the
  hood.
* fixed timer keybinds such that you can only trigger one phase change
  with a single press and release.