feat: oidc-client.js based Svelte OidcComponent

follows a pattern similar to @dopry/svelte-auth0,
but uses the more standards compliant oidc-client.js
library.

rollup.config.showcase.js

@@ -0,0 +1,66 @@
+import replace from '@rollup/plugin-replace';
+import pkg from './package.json';
+import commonjs from 'rollup-plugin-commonjs';
+import livereload from 'rollup-plugin-livereload';
+import resolve from 'rollup-plugin-node-resolve';
+import svelte from 'rollup-plugin-svelte';
+
+const production = !process.env.ROLLUP_WATCH;
+
+const defaultRedirectUri = production ? 'https://darrelopry.com/svelte-auth0' : 'http://localhost:5000/';
+const defaultPostLogoutRedirectUri = production ? 'https://darrelopry.com/svelte-auth0' : 'http://localhost:5000/';
+
+export default {
+	input: 'src/main.js',
+	output:  { sourcemap: true,	format: 'iife',	name: 'app', file: 'public/bundle.js'  },
+	plugins: [
+		replace({
+			'process.env.OIDC_ISSUER': process.env.OIDC_ISSUER || "https://dev-hvw40i79.auth0.com",
+			'process.env.OIDC_CLIENT_ID': process.env.OIDC_CLIENT_ID || "aOijZt2ug6Ovgzp0HXdF23B6zxwA6PaP",
+			'process.env.OIDC_REDIRECT_URI': process.env.OIDC_REDIRECT_URI ||  defaultRedirectUri,
+			'process.env.OIDC_POST_LOGOUT_REDIRECT_URI': process.env.OIDC_POST_LOGOUT_REDIRECT_URI ||  defaultPostLogoutRedirectUri,
+			'pkg.version': pkg.version
+		}),
+		svelte({ dev: true }),
+		resolve({
+			browser: true,
+			dedupe: (importee) =>
+				importee === 'svelte' || importee.startsWith('svelte/'),
+		}),
+		commonjs({
+			include: ['node_modules/**'],
+		}),
+
+		// In dev mode, call `npm run start` once
+		// the bundle has been generated
+		!production && serve(),
+
+		// Watch the `public` directory and refresh the
+		// browser on changes when not in production
+		!production && livereload('public'),
+	],
+	watch: {
+		clearScreen: false,
+	},
+};
+
+function serve() {
+	let started = false;
+
+	return {
+		writeBundle() {
+			if (!started) {
+				started = true;
+
+				require('child_process').spawn(
+					'npm',
+					['run', 'start', '--', '--dev'],
+					{
+						stdio: ['ignore', 'inherit', 'inherit'],
+						shell: true,
+					}
+				);
+			}
+		},
+	};
+}