support different pyodide versions (#328)

* add PyLoader class

* create global loader during app creation time and remove it when pyscript loading operations are done

* make the loader global and open/close when apps is starting. Also add concept of app config so users can set if they want to autoclose the loader of handle it themselves

* add pyconfig file

* auto add global config if there's no config set in the page

* export initializer type

* define type for config

* move initialization out of svelte file, into app config

* change runtimes from strings to objects

* fix typo

pyscriptjs/src/interpreter.ts

@@ -3,11 +3,12 @@ import { getLastPath } from './utils';
 let pyodideReadyPromise;
 let pyodide;
 
-const loadInterpreter = async function (): Promise<any> {
+const loadInterpreter = async function (indexUrl:string): Promise<any> {
     console.log('creating pyodide runtime');
     // eslint-disable-next-line
     // @ts-ignore
     pyodide = await loadPyodide({
+        // indexURL: indexUrl,
         stdout: console.log,
         stderr: console.log,
         fullStdLib: false