[Epic][Improvement] Improve written project documentation

[JamesKunstle]

We currently have minimal docs covering training rationale, interesting optimizations, or longer term objectives, nor do we currently link to the resources that already exist (e.g. the padding-free Transformers blog post).

We should collect all the resources we have and any brain-dump-grade information we care to share into some public set.

[github-actions]

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