Improve modal accessibility

Implement initial focus for modals. Change all modals including forms to put initial focus on the first input. When Enter is pressed on any input (CTRL + Enter for Textareas), the form is submitted if it is valid.

Co-authored-by: Sebastian Sdorra <sebastian.sdorra@cloudogu.com>
Co-authored-by: Eduard Heimbuch <eduard.heimbuch@cloudogu.com>

scm-ui/ui-components/.storybook/main.js

@@ -27,11 +27,14 @@ const fs = require("fs");
 const MiniCssExtractPlugin = require("mini-css-extract-plugin");
 const RemoveThemesPlugin = require("./RemoveThemesPlugin");
 const WorkerPlugin = require("worker-plugin");
+const ReactDOM = require("react-dom");
 
 const root = path.resolve("..");
 
 const themedir = path.join(root, "ui-styles", "src");
 
+ReactDOM.createPortal = node => node;
+
 const themes = fs
   .readdirSync(themedir)
   .map(filename => path.parse(filename))
@@ -50,7 +53,7 @@ module.exports = {
     // add our themes to webpack entry points
     config.entry = {
       main: config.entry,
-      ...themes,
+      ...themes
     };
 
     // create separate css files for our themes