LH2: send map size with computed locations

[aabadie]

What remains to do:

• add the missing tests
  - add the missing UI in the web page

[codecov-commenter]

Codecov Report

❌ Patch coverage is 91.17647% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.07%. Comparing base (c57d8aa) to head (236a5c5).
⚠️ Report is 436 commits behind head on main.

Files with missing lines	Patch %	Lines
dotbot/lighthouse2.py	62.50%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #98      +/-   ##
==========================================
+ Coverage   76.71%   77.07%   +0.36%     
==========================================
  Files          18       18              
  Lines        1559     1588      +29     
==========================================
+ Hits         1196     1224      +28     
- Misses        363      364       +1     

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[aabadie]

This is no longer WIP

[aabadie]

This PR is outdated and is now superseded by #202