Bundling external diagrams

[sidharthv96]

Is your feature request related to a problem? Please describe.
With the new lazyLoadedDiagrams, there is the requirement for an extra web request to fetch diagrams.
This might not be feasible in all environments (corporate firewalls, plugin limitations, etc).

Describe the solution you'd like
We should allow an option to pass diagrams directly to mermaid so it can avoid the network call.
This way, external diagrams could be bundled in at build time (if needed), reducing the time to load.

Describe alternatives you've considered
None

Additional context
We could also release versions of mermaid with different diagrams bundled.