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 Job ID Name Coverage
  Test
passed #6700
fp-timing
build-coq.8.6.1

00:05:28

passed #6699
fp-timing
build-coq.8.7.0

00:04:56