[doc] add dummy documentation for roi selection

3 jobs for fix_5 in 4 minutes and 32 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #41884
test:python3.5-stretch-pyqt5

00:04:32

passed #41885
test:python3.5-stretch-pyside2

00:04:09

passed #41886
test:test-xas-tutorials

00:04:13