Replace links in contributing page

[avallecam]

Some links in the contributing page have dead ends:

• bug reports --> could redirect to specific issue or choose site
• feature request --> could redirect to specific issue or choose site
• pull request template --> could redirect to PR template

However, this behaviour is also present in the epiparameter package contributing page

So, Is this something that should be solved in the packagetemplate?

[pratikunterwegs]

Flagging this for @joshwlambert's attention as well since {epiparameter} reportedly has the same issue.