[Leitwolf11]

Link the Tazel page to the Tazel repository

Tazel moved out of Progmasoft/tala into Progmasoft/tazel (tala#93), so
the "Source" link at the end of the Tazel landing page pointed at a
directory that no longer exists. In all four languages it now opens
https://github.com/Progmasoft/tazel. The Tala and Talac pages keep
their links into Progmasoft/tala.

[Leitwolf11]

Self-review from the diff: a new constant tazelRepository (https://github.com/Progmasoft/tazel) replaces ${repository}/tree/main/Tazel in the "Source" link of the Tazel landing page in all four locales (en-US, de-DE, ru-RU, he-IL). That directory left Progmasoft/tala in tala#93, so the old link would 404. The Tala and Talac links are unchanged. Frontend tests pass (42 pass, 2 skipped) and every check is green.