Consolidate issue tracking

[tordans]

I find it very confusing to find the right issue on all those OAM projects.

I suggest consolidating the issues in this repos.

Possible steps could be:

1. move all issues from the hotosm/OAM-* repos here (Github has a move feature for that)
2. add an issue template here which has a separate issue template for each of the sub project, which allows to auto-label the issues and to suggest a headline prefix like [oam-api]
3. add an issue template to all the other repos, which only has a link to the corresponding issue form on this repo; disable the "create issue without template" on those repos. Alternatively, disable issues completely and link here from the readmes.
4. update the readmes to clarify that all issues are collected in one place; including here, which