Update Tokens Tutorials

[nguyer]

This PR adds two brand new tutorials for ERC-20 and ERC-721 as well as how to use Metamask with them. It also includes some updates to the ERC-1155 tutorial to include approvals.

A live preview of the new docs pages can be found at: https://nguyer.github.io/firefly/tutorials/tokens

[codecov-commenter]

Codecov Report

Merging #777 (54f3dc4) into main (ea38e01) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##              main      #777   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          323       323           
  Lines        20181     20195   +14     
=========================================
+ Hits         20181     20195   +14     

Impacted Files	Coverage Δ
internal/events/aggregator.go	100.00% <0.00%> (ø)
internal/events/event_dispatcher.go	100.00% <0.00%> (ø)
internal/tokens/fftokens/fftokens.go	100.00% <0.00%> (ø)
internal/orchestrator/orchestrator.go	100.00% <0.00%> (ø)
internal/blockchain/ethereum/config.go	100.00% <0.00%> (ø)
internal/events/subscription_manager.go	100.00% <0.00%> (ø)
internal/blockchain/ethereum/ethereum.go	100.00% <0.00%> (ø)
internal/definitions/definition_handler.go	100.00% <0.00%> (ø)
internal/blockchain/ethereum/eventstream.go	100.00% <0.00%> (ø)
internal/apiserver/route_post_token_approval.go	100.00% <0.00%> (ø)
... and 3 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ea38e01...54f3dc4. Read the comment docs.

[awrichar]

This is awesome 🔥

[awrichar]

Requested a few changes inline. Some comments may apply across multiple pages since they're all fairly similar.

[awrichar]

One more minor note, but marking approved at this point. Thanks for pulling this together!