Add collaborators names (#1223)

* add random usernames

* add username state

* add username input

* ability to set names

* fix tests

* set username oon mobile

* remove auto generated names

* remove commented code

* always string

* updaate snapshots

* maintain username when clearing canvas

* Update src/renderer/renderScene.ts

Co-Authored-By: Lipis <lipiridis@gmail.com>

* add border

* fix styles

Co-authored-by: Pete Hunt <petehunt@users.noreply.github.com>
Co-authored-by: Faustino Kialungila <faustino.kialungila@gmail.com>
Co-authored-by: Lipis <lipiridis@gmail.com>

src/appState.ts

@@ -29,6 +29,7 @@ export function getDefaultAppState(): AppState {
     cursorButton: "up",
     scrolledOutside: false,
     name: `excalidraw-${getDateTime()}`,
+    username: "",
     isCollaborating: false,
     isResizing: false,
     isRotating: false,