Update Video Frame Metadata registration requirements (#924)

Add requirement for implementer support

Author: chrisn

video_frame_metadata_registry.src.html

@@ -24,8 +24,18 @@
 Registration Entry Requirements {#registration-entry-requirements}
 ==================================================================
 
-A registration entry is a document describing one or several metadata entries,
-and has the following requirements:
+To register an entry, file an issue in the
+[WebCodecs GitHub issue tracker](https://github.com/w3c/webcodecs/issues/)
+so it can be discussed and evaluated for compliance before being added to
+the registry.
+
+For the entry to be included, there needs to be interest from at least
+one implementer in either the Media Working Group or the Working Group that
+originated the registration entry specification. If the Media Working Group
+reaches consensus to accept the candidate entry, send a pull request
+(either by editors or by the party requesting the candidate registration)
+that meets the following requirements:
+
 1. Each metadata entry is defined as a separate {{VideoFrameMetadata}}
     dictionary member.
 2. Each metadata entry must be serializable.
@@ -34,19 +44,17 @@
 4. The specification defining each metadata entry must provide clearly defined
     semantics. In particular, interactions with the media processing pipeline
     (encoders, decoders, renderers, etc.) should be well defined.
-5. A candidate registration entry must be announced by filing an issue in the
-    WebCodecs GitHub issue tracker so they can be discussed and evaluated for
-    compliance before being added to the registry. If the Media Working Group
-    reaches consensus to accept the candidate, a pull request should be drafted
-    (either by editors or by the party requesting the candidate registration)
-    to register the candidate. The registry editors will review and merge the
-    pull request.
-6. Existing entries may be changed after being published, through the same
-    process as candidate entries. Possible changes include modification of
-    the link to the public specification.
-7. Existing entries may be deprecated. This requires Media Working Group
-    consensus, and if still active, consensus of the Working Group that
-    originated the registration entry specification.
+
+Once consensus is reached by the Media Working Group, the registry editors
+will review and merge the pull request.
+
+Existing entries may be changed after being published, through the same
+process as candidate entries. Possible changes include modification of the
+link to the public specification.
+
+Existing entries may be deprecated. This requires Media Working Group
+consensus, and if still active, consensus of the Working Group that
+originated the registration entry specification.
 
 
 VideoFrameMetadata members {#videoframemetadata-members}