Rollup merge of #52946 - Ajacmac:doc-impl-from, r=GuillaumeGomez

Documented impl From on line 367 of libserialize/json.rs

This is for the impl From mentioned in #51430 assigned to @skade .

Hopefully I didn't miss anything/get anything wrong. I looked over another PR for another part of this same issue to see what the proper formatting was, etc.

Thanks!

src/libserialize/json.rs

@@ -365,6 +365,9 @@ impl std::error::Error for EncoderError {
 }
 
 impl From<fmt::Error> for EncoderError {
+    /// Converts a [`fmt::Error`] into `EncoderError`
+    ///
+    /// This conversion does not allocate memory.
     fn from(err: fmt::Error) -> EncoderError { EncoderError::FmtError(err) }
 }