Improve UX of importing vs. opening files (#3661)

* wip

* fix drag and drop

* fix

* fix tests

* fix tests

* fix warning

* Partial code review

* add dialog

* fix web

* fix web

* push back release candidate expiry

* Code review

* Reduce code duplication for pasting files in frontend

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

editor/src/messages/frontend/frontend_message.rs

@@ -107,7 +107,6 @@ pub enum FrontendMessage {
 		font: Font,
 		url: String,
 	},
-	TriggerImport,
 	TriggerPersistenceRemoveDocument {
 		#[serde(rename = "documentId")]
 		document_id: DocumentId,
@@ -122,7 +121,8 @@ pub enum FrontendMessage {
 	TriggerLoadRestAutoSaveDocuments,
 	TriggerOpenLaunchDocuments,
 	TriggerLoadPreferences,
-	TriggerOpenDocument,
+	TriggerOpen,
+	TriggerImport,
 	TriggerSavePreferences {
 		preferences: PreferencesMessageHandler,
 	},