doc, tools: Start exploration of dictionaries
Context
This MR starts documenting some ways to estimate the number of solutions, given a grid and a dictionary.
This is basically paraphasing a '92 paper by Chris Long and Jensen's thesis in a way that makes sense to me.
Closes #64 (closed). (Other ticket will be created for the generic estimation by Harris and Forster. I haven't managed to get a copy of their papers yet.)
What has changed?
Main Changes
doc
- Add "Why dictionaries matter" (title is a bit dramatic but I like it)
tools
- Add a tool to compute the estimated number of solutions for square grids as formulated by Long
- Add a tool to compute the number of crossings between words of a dictionary - not very useful on real dictionaries, but keeping it nevertheless