Add copy chat message feature in Chat panel and enable usage in 'use chat copy' setting.

- Added 'copied' string to language translation in multiple translations file.
- Added 'CopyIcon' to svelte import.
- Defined a new status message variable in Chat.svelte.
- Created a new function 'setStatusMessage' to display the current panel's state after certain action.
- Added a new setting 'useChatCopy' in 'DisplaySettings.svelte'.
- Created a checkbox with label 'useChatCopy' to toggle the Chat message copy.
- Integrated Clipboard API in Chat code to handle chat message copy via button click.

src/lang/en.ts

@@ -304,5 +304,7 @@ export const languageEnglish = {
     shareCloud: "Share to RisuRealm",
     hub: "RisuRealm",
     tags: "Tags",
-    backgroundHTML: "Background Embedding"
+    backgroundHTML: "Background Embedding",
+    copied: "Copied",
+    useChatCopy: "Use Chat Message Copy",
 }