Start the punctuation chapter

This is just a stub, with the expectation that it will be
expanded/rewritten later.

Author: ehuss

contributor-guide/src/SUMMARY.md

@@ -19,6 +19,6 @@
 - [Style guide](style/index.md)
     - [Wording](style/wording.md)
     - [Language and grammar]()
-    - [Punctuation]()
+    - [Punctuation](style/punctuation.md)
 - [Review policy](review-policy.md)
 - [Resources]()

contributor-guide/src/style/punctuation.md

@@ -0,0 +1,5 @@
+# Punctuation
+
+Use Oxford commas.
+
+Avoid slashes for alternatives ("program/binary"); use conjunctions or rewrite it ("program or binary").

docs/authoring.md

@@ -4,13 +4,6 @@ This document serves as a guide for editors and reviewers. Some conventions and
 
 [introduction]: ../src/introduction.md
 
-## Style
-
-Idioms and styling:
-
-* Use Oxford commas.
-* Avoid slashes for alternatives ("program/binary"); use conjunctions or rewrite it ("program or binary").
-
 ## Content guidelines
 
 The following are guidelines for the content of the reference.