Plots2: API tagging implementation

[stefannibrasil]

The goal of this Issue is to improve #1934, as discussed in #2755.

We need to include tags in the URL input. This should solve #2254.

Steps

• [x] Include tags in URL: https://github.com/publiclab/plots2/blob/46f3d43a73f727a547f737a401ae76411d3c2ef6/app/api/srch/search.rb#L118-L119

• [x] Update the nearbyNodes method to also include tags:
  https://github.com/publiclab/plots2/blob/46f3d43a73f727a547f737a401ae76411d3c2ef6/app/services/search_service.rb#L188

• [ ] Update doc/API.md file with the new functionality

[stefannibrasil]

@Gauravano @sagarpreet-chadha @jywarren I've written this Issue to coordinate better our contribution. I am working on this, I just need more time to configure my PC again because I've updated my OS :smile: