Add alt text support and rework image layout (#503)

* Add alt text support and rework image layout

* Add additional BottomSheet implementation to account for nested Composer modal

* Use mobile gallery layout on mobile web

* Missing key

* Fix lint

* Move altimage modal into the standard modal system

* Fix overflow wrapping of images

* Fixes to the alt-image modal

* Remove unnecessary switch

* Restore old imagelayoutgrid code

---------

Co-authored-by: Paul Frazee <pfrazee@gmail.com>

src/lib/media/alt-text.ts

@@ -0,0 +1,16 @@
+import {RootStoreModel} from 'state/index'
+
+export async function openAltTextModal(store: RootStoreModel): Promise<string> {
+  return new Promise((resolve, reject) => {
+    store.shell.openModal({
+      name: 'alt-text-image',
+      onAltTextSet: (altText?: string) => {
+        if (altText) {
+          resolve(altText)
+        } else {
+          reject(new Error('Canceled'))
+        }
+      },
+    })
+  })
+}