Expose utility functions for clientside callbacks to use

[KoolADE85]

When writing client-side callbacks (or any client side javascript), it would be nice to have access to utility functions from the dash renderer.

Things like:

• retrieving components by their ID, type, and/or property
• constructing/deconstructing the string version of pattern-matching IDs
• testing whether a pattern-matching ID matches a given pattern

would be less prone to bugs if devs can directly use the same code that Dash itself uses.

These could be exposed as helper functions on the window, or as a React context.