add comment regarding support of Markdown files

Author: PhilippSalvisberg

README.md

@@ -108,10 +108,12 @@ options:
 
 Please note that db\* CODECOP applies by default a filter to support the following file extensions: `.sql`, `.prc`, `.fnc`, `.pks`, `.pkb`, `.trg`, `.vw`, `.tps`, `.tpb`, `.tbp`, `.plb`, `.pls`, `.rcv`, `.spc`, `.typ`, `.aqt`, `.aqp`, `.ctx`, `.dbl`, `.tab`, `.dim`, `.snp`, `.con`, `.collt`, `.seq`, `.syn`, `.grt`, `.sp`, `.spb`, `.sps`, `.pck`, `.md`, `.mdown`. To process other or additional file extensions, you must pass your own filter expression.
 
-The value of all options will be included in the output files and on the console output.
+For Markdown files only the code within SQL code blocks is analyzed. If other file extensions than `.md` and `.mdown` are used then the content must start with a `#` to be identified as a Markdown file.
 
 Guideline checks can be disabled when implementing a validator. When the `skip` option is not defined then all disabled guideines are skipped. To enable all checks pass `skip=none`.
 
+The value of all options will be included in the output files and on the console output.
+
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