webp-container-spec.txt: update 'key words' text
RFC 2119 was updated by RFC 8174; use the text from there
+ change INFORMATIVE to informative to avoid confusion with the key
words in the RFCs
@@ -46,9 +46,10 @@ for:
* **Animation.** An image may have multiple frames with pauses between them,
making it an animation.
-The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
-"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
-document are to be interpreted as described in [RFC 2119][].
+The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
+"SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this
+document are to be interpreted as described in BCP 14 [RFC 2119][] [RFC 8174][]
+when, and only when, they appear in all capitals, as shown here.
Bit numbering in chunk diagrams starts at `0` for the most significant bit
('MSB 0') as described in [RFC 1166][].
@@ -531,7 +532,7 @@ Reserved (Rsv): 2 bits
Pre-processing (P): 2 bits
-: These INFORMATIVE bits are used to signal the pre-processing that has
+: These _informative_ bits are used to signal the pre-processing that has
been performed during compression. The decoder can use this information to
e.g. dither the values or smooth the gradients prior to display.
@@ -817,3 +818,4 @@ RIFF/WEBP
[metadata]: https://web.archive.org/web/20180919181934/http://www.metadataworkinggroup.org/pdf/mwg_guidance.pdf
[rfc 1166]: https://datatracker.ietf.org/doc/html/rfc1166
[rfc 2119]: https://datatracker.ietf.org/doc/html/rfc2119
+[rfc 8174]: https://datatracker.ietf.org/doc/html/rfc8174
