Standardize architectural diagrams style

[ginny-d]

• Gather all images
• Create a unique consistent style

Examples (of what shouldn't happen):

[ginny-d]

Found diagrams:

https://docs.hiro.so/stacks-blockchain-api/overview
https://docs.hiro.so/subnets/overview
https://docs.hiro.so/token-metadata-api/overview

[elenananana]

another one

[ryanwaits]

closing, combined with #502

[ginny-d]

[ginny-d]

closing, combined with #502

Reopening, this issue addresses graphs already in existence. The other issue requests new graphs.

[ginny-d]

@ryanwaits Here are the updated architecture diagrams that are currently on Docs. These are on SVG so they work both on light and dark mode.

These graphs can be found at https://docs.hiro.so/stacks/api/architecture and https://docs.hiro.so/stacks/token-metadata-api/architecture

I didn't find any other graphs on the site, but let me know if I missed any!