Add the Help > About Graphite dialog with build info

Closes #404

editor/src/document/document_message_handler.rs

@@ -25,6 +25,7 @@ pub enum DocumentsMessage {
 	CloseActiveDocumentWithConfirmation,
 	CloseAllDocumentsWithConfirmation,
 	CloseAllDocuments,
+	RequestAboutGraphiteDialog,
 	NewDocument,
 	OpenDocument,
 	OpenDocumentFile(String, String),
@@ -124,6 +125,9 @@ impl MessageHandler<DocumentsMessage, &InputPreprocessor> for DocumentsMessageHa
 		use DocumentMessage::*;
 		use DocumentsMessage::*;
 		match message {
+			RequestAboutGraphiteDialog => {
+				responses.push_back(FrontendMessage::DisplayAboutGraphiteDialog.into());
+			}
 			Document(message) => self.active_document_mut().process_action(message, ipp, responses),
 			SelectDocument(index) => {
 				// NOTE: Potentially this will break if we ever exceed 56 bit values due to how the message parsing system works.

editor/src/frontend/frontend_message_handler.rs

@@ -15,6 +15,7 @@ pub enum FrontendMessage {
 	DisplayPanic { panic_info: String, title: String, description: String },
 	DisplayConfirmationToCloseDocument { document_index: usize },
 	DisplayConfirmationToCloseAllDocuments,
+	DisplayAboutGraphiteDialog,
 	UpdateLayer { data: LayerPanelEntry },
 	UpdateCanvas { document: String },
 	UpdateScrollbars { position: (f64, f64), size: (f64, f64), multiplier: (f64, f64) },
@@ -22,8 +23,6 @@ pub enum FrontendMessage {
 	ExportDocument { document: String, name: String },
 	SaveDocument { document: String, name: String },
 	OpenDocumentBrowse,
-	EnableTextInput,
-	DisableTextInput,
 	UpdateWorkingColors { primary: Color, secondary: Color },
 	SetCanvasZoom { new_zoom: f64 },
 	SetCanvasRotation { new_radians: f64 },