added BCH Guru wave2 metadata

[bchguru]

Added metadata snapshot for BCH Guru to include wave 2 NFT metadata as discussed in issue #10 .

This metadata is also the current authHead for the BCHGURU identity (txid 0e273099d062afb45afad0289f6740232ab3ae864e20534e44cf5201d315c30b)

[bitjson]

Reviewed, looks great, thanks for the careful work @bchguru! This PR also doesn't need another reviewer – @bchguru is a previous contributor, so I was the second review. Merging 🚀

I'll note there are a few minimal changes to existing extensions.attributes, e.g.

"extensions": {
                    "attributes": {
-                     "Background": "Lime Burst Gradient",
+                     "Background": "Lime Burst",
// ...

I verified that those changes exist in the on-chain metadata too.

By the way @bchguru, I just invited you to the Reviewer team here on the GitHub.

(Repo note: this PR follows discussion initiated by @bchguru about OTR's policy for historical metadata: #10)