doc: Add a link to clang-format file for QtCreator

Author: 10110111

doc/codingConventions.doxygen

@@ -25,7 +25,10 @@
 
 The increasing number of contributors require that we clearly define coding rules and guidelines. Although for historical reasons the current code of Stellarium does not always comply to these rules, they should now be respected for any addition or modification of the code.
 
-Settings for <a href="http://doc.qt.io/qtcreator/index.html">QtCreator</a> IDE you can get <a href="stellarium-ide.xml">here</a>.
+For <a href="http://doc.qt.io/qtcreator/index.html">QtCreator</a> IDE you can find the settings below. Note that to have the ClangFormat settings work as expected you need to disable *Clean whitespace* in *Preferences* → *Text Editor* → *Behavior* → *Cleanups Upon Saving*, otherwise editing will work fine, but saving will reset the formatting of the file to a wrong state.
+ - <a href="https://github.com/Stellarium/stellarium/blob/master/.clang-format">ClangFormat config file</a> for QtCreator ≥ 13,
+ - <a href="stellarium-ide.xml">Legacy XML file</a> for the built-in indentor of QtCreator < 13.
+
 
 @section stylistic_conventions_sec Stylistic Conventions
  - Source code should use the ASCII character set. Characters such as '&egrave;'