refactor(cheddar): Support multiple shortlinks & custom link sets r/2835

This makes it possible for users of cheddar as a library to supply
their own shortlinks. In practice it is unlikely anyone will do this,
but the change also allows us to (relatively) easily add additional
shortlinks to the set used by TVL.

Note that Cheddar is primarily intended for use by TVL and the default
rendering function interfaces have not changed, and will default to
using TVL shortlinks.

A new public function `format_markdown_with_shortlinks` has been added
with which users can use an alternative set of shortlinks. This
function should not be used in TVL depot code.

Change-Id: I4ddab28cbcf45d07c51323b7b730b96e62922816
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3083
Tested-by: BuildkiteCI
Reviewed-by: lukegb <lukegb@tvl.fyi>

0 files changed, 0 insertions, 0 deletions