Remove reference to 'username' and update descriptions in metadata (#1726)

Author: dtonon

01.md

@@ -89,7 +89,7 @@ Kinds specify how clients should interpret the meaning of each event and the oth
 
 This NIP defines one basic kind:
 
-- `0`: **user metadata**: the `content` is set to a stringified JSON object `{name: <username>, about: <string>, picture: <url, string>}` describing the user who created the event. [Extra metadata fields](24.md#kind-0) may be set. A relay may delete older events once it gets a new one for the same pubkey.
+- `0`: **user metadata**: the `content` is set to a stringified JSON object `{name: <nickname or full name>, about: <short bio>, picture: <url of the image>}` describing the user who created the event. [Extra metadata fields](24.md#kind-0) may be set. A relay may delete older events once it gets a new one for the same pubkey.
 
 And also a convention for kind ranges that allow for easier experimentation and flexibility of relay implementation: