Implement ctrl-shift click to select multiple documents (#1851)

* Initial implementation of shift and ctrl click to select

* Implement shift-ctrl selection

* Fix snapshot, update selectionHelper comment

* Fix missing type

* Properly disable cursor selection

* Update snapshots

* Do not enable (multiselect) if readonly

* Consider meta key for mac and ctrl for everything else

src/Utils/KeyboardUtils.ts

@@ -0,0 +1,15 @@
+/**
+ * Is the environment 'ctrl' key press. This key is used for multi selection, like select one more item, select all.
+ * For Windows and Linux, it's ctrl. For Mac, it's command.
+ */
+export const isEnvironmentCtrlPressed = (event: JQueryEventObject | React.MouseEvent): boolean =>
+  isMac() ? event.metaKey : event.ctrlKey;
+
+export const isEnvironmentShiftPressed = (event: JQueryEventObject | React.MouseEvent): boolean => event.shiftKey;
+
+export const isEnvironmentAltPressed = (event: JQueryEventObject | React.MouseEvent): boolean => event.altKey;
+
+/**
+ * Returns whether the current platform is MacOS.
+ */
+export const isMac = (): boolean => navigator.platform.toUpperCase().indexOf("MAC") >= 0;