Add new POI category icons

[MizukiTemma]

Short description

This PR adds two new POI category icons (mental health and shelter)

Proposed changes

• Add constants and svg files for the new icons
• (Still in clearing: adjust API response, see the issue page)

Side effects

• What should be the german translation of "shelter"? Is it "Shelter" in German too? 😁

Resolved issues

Fixes: #2698

---

Pull Request Review Guidelines

[codeclimate[bot]]

Code Climate has analyzed commit 007756e1 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 81.8% (0.0% change).

View more on Code Climate.

[lunars97]

I think Unterkunft is a suitable word for shelter :)

[JoeyStk]

What should be the german translation of "shelter"? Is it "Shelter" in German too? 😁

I think "Unterkunft" certainly is an option, but in this case I'd probably prefer "Obdach" as it seems to have an immediate connection to the "Vernetztes Obdach" project. But maybe @f1sh1918 can give us some additional context on what the best translation for "shelter" would be :)

[FritjofK]

@MizukiTemma and @JoeyStk Please use "Notunterkünfte" as the German translation for shelter. That is the exact wording that is desired for "VernetztesObdach".