add "double" into the list of built in QML types

Also this fixed "property type checking" for qmllint
in case of QML code like "property double xyz"

Fixes: QTBUG-92566
Change-Id: Ice33be4287ce0eba2cf9dfaabb760406bdca02b7
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

src/imports/builtins/builtins.qmltypes

@@ -108,7 +108,7 @@ Module {
     Component {
         name: "double"
         prototype: "number"
-        exports: ["QML/real 1.0"]
+        exports: ["QML/real 1.0", "QML/double 1.0"]
         exportMetaObjectRevisions: [256]
         accessSemantics: "value"
     }

tests/auto/qml/qmllint/data/used.qml

@@ -13,4 +13,5 @@ Item {
     required property Something moo
     property bool boolVar: false
     property real realVar: 17.17
+    property double doubleVar: 18.18
 }