Add missing ~ operator to expression builder

resources/function_help/json/op_regex

@@ -0,0 +1,14 @@
+{
+  "name": "~",
+  "type": "operator",
+  "description": "Performs a regular expression match on a string value.",
+  "arguments": [
+        { "arg": "string", "description": "A string value" },
+        { "arg": "regex", "description": "A regular expression. Slashes must be escaped, eg \\\\\\\\d." }
+  ],
+  "examples": [
+	{ "expression":"'hello' ~ 'll'", "returns":"1"},
+	{ "expression":"'hello' ~ '^ll'", "returns":"0"},
+	{ "expression":"'hello' ~ 'llo$'", "returns":"1"}
+  ]
+}

src/gui/qgsexpressionbuilderwidget.cpp

@@ -453,6 +453,7 @@ void QgsExpressionBuilderWidget::updateFunctionTree()
   registerItem( QStringLiteral( "Operators" ), QStringLiteral( "%" ), QStringLiteral( " % " ) );
   registerItem( QStringLiteral( "Operators" ), QStringLiteral( "^" ), QStringLiteral( " ^ " ) );
   registerItem( QStringLiteral( "Operators" ), QStringLiteral( "=" ), QStringLiteral( " = " ) );
+  registerItem( QStringLiteral( "Operators" ), QStringLiteral( "~" ), QStringLiteral( " ~ " ) );
   registerItem( QStringLiteral( "Operators" ), QStringLiteral( ">" ), QStringLiteral( " > " ) );
   registerItem( QStringLiteral( "Operators" ), QStringLiteral( "<" ), QStringLiteral( " < " ) );
   registerItem( QStringLiteral( "Operators" ), QStringLiteral( "<>" ), QStringLiteral( " <> " ) );