Make REUSE requirement more concrete

[cornelius]

We should add some more details to the REUSE requirement in the incubation stage (see https://github.com/OpenRailAssociation/technical-committee/blob/main/meetings/2024-09-17.md):

Add to the questionnaire, that the REUSE linter has to run and be green, and that the DCO bot has to be enabled. Plus link to documentation of the project in CONTRIBUTING.md that REUSE and DCO are required. REUSE badge in the project would be an additional option.