feat: Modal + ViewportDownloadForm (#1799)

* feat: Modal + ViewportDownloadForm

* styles for image preview box

* modal update & close handler

* open modal for Learn More (search info)

* change modal default alignment

* Update platform/ui/src/components/InputNumber/InputNumber.mdx

* nuke inputNumber and use inputText with refactor

* make input more reusable

* revert inputText "number" stuff

* replace inputText to Input

* fix input spacing + label

* fix modal overlay classes

* fix inline styles

* fix onclick learn more

* fix close icon

* revert transition

* remove inline styles

* remove unecessary stuff

extensions/cornerstone/src/CornerstoneViewportDownloadForm.js

@@ -145,8 +145,4 @@ CornerstoneViewportDownloadForm.propTypes = {
   activeViewportIndex: PropTypes.number.isRequired,
 };
 
-// export default CornerstoneViewportDownloadForm;
-
-export default function HelloWorld() {
-  return <div>Hello World</div>;
-}
+export default CornerstoneViewportDownloadForm;