remove backticks, add metadata

Co-authored-by: Chris Markiewicz <effigies@gmail.com>

src/common-principles.md

@@ -6,14 +6,14 @@ The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
 "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
 interpreted as described in [[RFC2119](https://www.ietf.org/rfc/rfc2119.txt)].
 
-Based on these keywords, we define three requirement levels for specifying data:
-`REQUIRED`, `RECOMMENDED`, and `OPTIONAL`.
+Based on these keywords, we define three requirement levels for specifying data or metadata:
+REQUIRED, RECOMMENDED, and OPTIONAL.
 The guiding principles for when particular data is placed under a given requirement level
 can be loosely described as below:
 
-* `REQUIRED`: Data cannot be be interpreted without this information (or the ambiguity is unacceptably high)
-* `RECOMMENDED`: Interpretation/utility would be dramatically improved with this information
-* `OPTIONAL`: Users and/or tools might find it useful to have this information
+* REQUIRED: Data cannot be be interpreted without this information (or the ambiguity is unacceptably high)
+* RECOMMENDED: Interpretation/utility would be dramatically improved with this information
+* OPTIONAL: Users and/or tools might find it useful to have this information
 
 Throughout this specification we use a list of terms and abbreviations.
 To avoid misunderstanding we clarify them here.