issue #8902 markdown: account for quotation marks before emphasis

Fixes rendering of text like:

    This entire quote should be bold **"outside"**
    This entire quote should be bold italics ***"outside"***
    This entire quote should be italics *"outside"*

Author: Hi-Angel

src/markdown.cpp

@@ -85,7 +85,7 @@ enum class ExplicitPageResult
    c=='&' || c=='*' || c=='%' || \
    c=='[' || c=='(' || c=='.' || \
    c=='>' || c==':' || c==',' || \
-   c==';')
+   c==';' || c=='\'' || c=='"')
 
 // is character at position i in data allowed before an emphasis section
 #define isOpenEmphChar(c) \