Added CMOS quote for additional guidance on capitalization after colons

Author: Chris Cho

source/style-guide/style/punctuation.txt

@@ -60,6 +60,15 @@ Use the following guidelines for colons:
 - If a title or heading includes a colon, capitalize the first word
   that follows the colon, regardless of its part of speech.
 
+- "Lowercase or capital letter after a colon. When a colon is used within
+  a sentence, as in the first two examples in 6.61, the first word following
+  the colon is lowercased unless it is a proper noun.
+
+  When a colon introduces two or more sentences or when it introduces
+  speech in dialog or a quotation or question, the first word following
+  it is capitalized" (from Chicago Manual of Style 6.63, v.17).
+
+
 Commas
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