Syntax diagrams in user documentation

SQLite has a bubble generator tool that they use to generate syntax
diagrams for their documentation:

https://www.sqlite.org/docsrc/doc/tip/art/syntax/bubble-generator.tcl?mimetype=text/plain

I think that the results are rather good. See, for example, the INSERT
documentation:

https://www.sqlite.org/lang_insert.html

Now that we have infrastructure that can add images to our
documentation, we may want to consider something like this. Note that
Bison has an option that outputs a grammar as a Graphviz dot file:

https://www.gnu.org/software/bison/manual/html_node/Graphviz.html

It's probably not possible to create a useful visualization/syntax
diagram with Bison's --graph option, but it might at least be an
interesting starting point.

I don't think that it's necessary to discuss this now. This can be a
placeholder thread that we may come back to when we're all less busy.
-- 
Peter Geoghegan