doc: Add page describing how to build Upper Limits table (#57)

* Add rich to requirements.txt and rebuild lock file.
* Add notebook on procedure for building upper limits table common to
  search analyses.
* Add .DS_Store to .gitignore.

Co-authored-by: Matthew Feickert <matthew.feickert@cern.ch>

Author: kratsg

.gitignore

@@ -133,3 +133,6 @@ _build
 *.tar.gz
 book/data/
 book/1Lbb-likelihoods/
+
+# Mac artifacts
+.DS_Store

binder/requirements.txt

@@ -4,6 +4,7 @@ ipywidgets~=8.0.7
 ipympl~=0.9.3
 pandas~=2.0.3
 altair~=5.0.1
+rich==13.5.2
 # jupyter notebooks
 notebook>=7.0.0
 jupyterlab>=4.0.3