Move over wiki documentation to repo in Markdown format (#1760)

* Change in-client regex help link to point to the github repository

src/widgets/helper/EditableModelView.cpp

@@ -95,9 +95,10 @@ void EditableModelView::addCustomButton(QWidget *widget)
 
 void EditableModelView::addRegexHelpLink()
 {
-    auto regexHelpLabel =
-        new QLabel("<a href='https://chatterino.com/help/regex'><span "
-                   "style='color:#99f'>regex info</span></a>");
+    auto regexHelpLabel = new QLabel(
+        "<a href='"
+        "https://github.com/Chatterino/chatterino2/blob/master/docs/Regex.md'>"
+        "<span style='color:#99f'>regex info</span></a>");
     regexHelpLabel->setOpenExternalLinks(true);
     this->addCustomButton(regexHelpLabel);
 }