Add type annotations (#396)

* Add type annotations

* Replace `StateCommand` with `Command`

* Revert "Replace `StateCommand` with `Command`"

This reverts commit 2dfc2d34e4.

* Fix the return value

pyscriptjs/src/components/pyrepl.ts

@@ -32,16 +32,16 @@ mode.subscribe(value => {
     currentMode = value;
 });
 
-function createCmdHandler(el) {
+function createCmdHandler(el: PyRepl): StateCommand {
     // Creates a codemirror cmd handler that calls the el.evaluate when an event
     // triggers that specific cmd
-    const toggleCheckbox: StateCommand = ({ state, dispatch }) => {
-        return el.evaluate(state);
+    return () => {
+        void el.evaluate();
+        return true;
     };
-    return toggleCheckbox;
 }
 
-let initialTheme;
+let initialTheme: string;
 function getEditorTheme(el: BaseEvalElement): string {
     if (initialTheme) {
         return initialTheme;