Add App: Lobste.rs App

• The app complies with the inclusion criteria
• The original app author has been notified (and supports the inclusion)
• All related fdroiddata and rfp issues have been referenced in this merge request
• Builds with fdroid build

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I tried to build it on MacOS, and I can't build anything in the repo because

• it tries to use the deprecated android command
• the vagrant setup uses import vagrant which apparently doesn't exist on PyPi (even though I have vagrant installed)
• using fdroid build --server com.nikhiljha.lobstersapp errors with Couldn't open file /Users/nikhil/Dev/fdroiddata/builder/buildserver because it doesn't exist

This app is written using Flutter, so I shouldn't need the android command. Still it fails with...

ERROR: Could not build app com.nikhiljha.lobstersapp due to unknown error: Traceback (most recent call last):
  File "/usr/local/Cellar/fdroidserver/1.0.9/libexec/lib/python3.7/site-packages/fdroidserver/build.py", line 1120, in main
    options.onserver, options.refresh):
  File "/usr/local/Cellar/fdroidserver/1.0.9/libexec/lib/python3.7/site-packages/fdroidserver/build.py", line 896, in trybuild
    build_local(app, build, vcs, build_dir, output_dir, log_dir, srclib_dir, extlib_dir, tmp_dir, force, onserver, refresh)
  File "/usr/local/Cellar/fdroidserver/1.0.9/libexec/lib/python3.7/site-packages/fdroidserver/build.py", line 562, in build_local
    tarball.add(build_dir, tarname, exclude=tarexc)
TypeError: add() got an unexpected keyword argument 'exclude'

I think it should build (I basically copy-pasted another config), but I can't get it to build on my machine. Help would be appreciated.