Merge branch 'amin/spanning' into 'master'

Add the spanning tree algorithm.

Closes #3

See merge request FP/iris-examples!3
2 jobs for master in 5 minutes and 30 seconds (queued for 1 second)
Status Name Job ID Coverage
  Test
passed build-coq.8.6.1 #6700
fp-timing

00:05:28

passed build-coq.8.7.0 #6699
fp-timing

00:04:56