Replace all hardcoded urls with url tags in templates

[Baschdl]

Do you find something besides facebook, twitter, youtube and github?

[bjrne]

• For example 'matching/password_change' in the participant dashboard, I am sure that I have seen more.

[Baschdl]

Ah, you're referring to the question @maltezacharias already asked in https://github.com/match4everyone/match4everything/pull/105#discussion_r452454882