Add modern attachment mimetype icons

specifyweb/frontend/js_src/lib/components/Attachments/MimetypeIcons.d.ts

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+// Support importing SVG files as strings
+
+declare module '*.svg' {
+
+    const content: string;
+
+    export default content;
+}  

specifyweb/frontend/js_src/lib/components/Attachments/MimetypeIcons/LICENSE.md

@@ -0,0 +1,7 @@
+The mimetype icons originate from the Elementary icon theme:
+
+Link: https://github.com/elementary/icons
+Author: Members of the Elementary OS team (https://github.com/orgs/elementary/people)
+License: GPLv3 (https://choosealicense.com/licenses/gpl-3.0/)
+
+https://github.com/linuxmint/mint-l-icons/tree/master/src/mimetypes