Add sequence diagram

[OR13]

This PR addresses #13

[OR13]

Feel free to make adjustments using: https://mermaid.live/edit#pako:eNqNU01v2zAM_SuEztkf8KE7ZAWWw3ZYe9ngiyLRMRF9uBLlwij630fZFZatyTadZOq9R_KZfFEmWlSdyvhUMBj8RPqUtO8DyJl0YjI06cBwyLlgeh9_TDpkCQh5ecA0k8EN9DUygsOBIQ5v7A4OwPqMkDBPMWQ6kiNeYIgJeESosoM2nAU3pWhL09ro8OHu7lq-Dh5HzJWOq8wUnVSHVUV7MNF7YkYLHMEjMoXT_6keILMOFo4L-AWM0-Qz6GMsXL9bsZuWi3GC_QbZj2jOW7ieK9q3c37DmfBZDHI4V3tbVimjtbUpY7Db5ZZ8s_wzii2Ua8nCiSmjRxGuigkN0vTWwV5-SPGYhHvdjSzmik7rG7IesHpaMn68MOH-Ism_nbiV7S8-XHTxpxc3zWjNdfA9FjA6AKeS-feOduv0XJokj5nJOZi1o5ZjHexEp3Gd7F_KBxj1jDJvYSBbdwkovBtrs8HVTgnHa7Kyey9VuFcC9dirTq5Wp3Ov-vAqOF04PizBqE5Kxp0qk9Xc9lR1g3ZZomiJY_qyLfO60zsl-_kjxoZ5_QnpGWCo

Github comments support mermaid:

``` mermaid
...
```

sequenceDiagram
    participant Issuer
    participant TransparencyService
    Note left of Issuer: I take responsibility for the artifacts I produce
    Issuer ->> TransparencyService: These are the policies I am committed to meeting
    Issuer ->> TransparencyService: I stand by my claims about my artifact
    loop Claims Check
        TransparencyService ->> TransparencyService: Review relevant claims and policies
    end
    TransparencyService ->> Issuer: Here is my endorsement and receipt
    Consumer->>TransparencyService: Is this artifact safe to use?
    loop Endorsement Check
        TransparencyService->>TransparencyService: Review relevant claims and endorsements
    end
     TransparencyService ->> Consumer: You can trust this artifact, the endorsement is still valid
     Note right of Consumer: I have confidence in the artifacts I consume

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[SteveLasker]

@OR13, is this a draft PR?

[OR13]

Yes, of course... The svg build is currently bugging, I can't build the draft locally.

[OR13]

Animated nyancat for testing purposes only.

[aj-stein-nist]

Yes, of course... The svg build is currently bugging, I can't build the draft locally.

The last GHA build complains about mmdc.

/usr/lib/ruby/3.2.0/open3.rb:222:in `spawn': No such file or directory - mmdc (Errno::ENOENT)
	from /usr/lib/ruby/3.2.0/open3.rb:222:in `popen_run'
	from /usr/lib/ruby/3.2.0/open3.rb:103:in `popen3'
	from /usr/lib/ruby/3.2.0/open3.rb:290:in `capture3'

TIL is the name of the shorthand name of the mermaid-cli compiler. I did not know that. I am looking Martin Thompson's template repo to see if this is supported (it must be if it mapped the ```mermaid backticks to that presumably installed command or what the deal is.

EDIT: Perhaps this is the issue, we need our own package.json to activate that? It's implied, but kind of neat. I shall test.

[OR13]

closing for now, well need to do this with aasvg until other options become available.