Add .nvmrc

[paul121]

Closes #210

[paul121]

Appears to be working in github actions: https://github.com/farmOS/farmOS-map/actions/runs/15642933782/job/44074364398?pr=211

Run actions/setup-node@v4
  with:
    node-version-file: .nvmrc
    always-auth: false
    check-latest: false
    token: ***
Node version file is not JSON file
Resolved .nvmrc as 22.4.0
Attempting to download 22.4.0...
Acquiring 22.4.0 - x64 from https://github.com/actions/node-versions/releases/download/22.4.0-9766506602/node-22.4.0-linux-x64.tar.gz
Extracting ...
/usr/bin/tar xz --strip [1](https://github.com/farmOS/farmOS-map/actions/runs/15642933782/job/44074364398?pr=211#step:3:1) --warning=no-unknown-keyword --overwrite -C /home/runner/work/_temp/[2](https://github.com/farmOS/farmOS-map/actions/runs/15642933782/job/44074364398?pr=211#step:3:2)e34be21-7ce1-49a1-9[3](https://github.com/farmOS/farmOS-map/actions/runs/15642933782/job/44074364398?pr=211#step:3:3)df-329020fce893 -f /home/runner/work/_temp/389e190f-6f0b-[4](https://github.com/farmOS/farmOS-map/actions/runs/15642933782/job/44074364398?pr=211#step:3:4)cb4-91ef-fd7362641fc7
Adding to the cache ...
Environment details
  node: v22.4.0
  npm: 10.[8](https://github.com/farmOS/farmOS-map/actions/runs/15642933782/job/44074364398?pr=211#step:3:9).1
  yarn: 1.22.22

[mstenta]

Merged! Thanks @paul121!!