feat: blob protocol draft (#115)

Based on #114. PR is written with UCAN 1.0 format and assuming
storacha/RFC#12 however in terms of
immediate implementation I suggest that we instead

1. Use `blob/add` instead of `/space/content/add/blob`
2. Use `web3.storage/blob/*` in place of `/service/blob/` 

I suggest above because I think it would make more sense to transition
to storacha/RFC#12 once we have [email protected]
implemented, because I suspect links to tasks vs invocations are going
to be a pain to deal with otherwise. This will give us cleaner break.

In terms of implementing `/service/blob/accept` and specifically how
does client signal that they've completed upload I suggest that we do
whichever is easiest option from following two:

1. Make client sent second `blob/add` invocation after they've done
upload so we can perform a lookup.
2. Add another temp capability with empty output either very specific
like `blob/add/poll` or very general like `invocation/wake { task: CID }
`.

---------

Co-authored-by: Vasco Santos <[email protected]>

.github/workflows/words-to-ignore.txt

@@ -167,3 +167,5 @@ SHA2-256
 noop
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