Provide Statistics per-page

[stevan]

It would be nice to be able to display per-page statistics, such as:

• number of built-ins called
• number of packages loaded
• number of sub calls
• etc.

It would be a simple matter of asking jQuery to count the number of matching nodes for a given syntax CSS class, storing those counts somewhere and displaying them.

[stevan]

This could also be a good way to handle the tests in syntax-samples, if we add a comment detailing what kind of data we expect, then one could compare the stats to that expectation and know if something has been broken.