web: add markdown formatting keyboard shortcuts in composer

web/src/components/MessageComposer.tsx

@@ -525,6 +525,41 @@ export function MessageComposer() {
   }, [gifQuery, showGifMenu]);
 
   function onComposerKeyDown(event: KeyboardEvent<HTMLTextAreaElement>) {
+    const hasModifier = event.ctrlKey || event.metaKey;
+    if (hasModifier) {
+      const key = event.key.toLowerCase();
+      if (key === "b") {
+        event.preventDefault();
+        insertFormatting("**", "**");
+        return;
+      }
+      if (key === "i") {
+        event.preventDefault();
+        insertFormatting("*", "*");
+        return;
+      }
+      if (key === "u") {
+        event.preventDefault();
+        insertFormatting("__", "__");
+        return;
+      }
+      if (key === "k") {
+        event.preventDefault();
+        insertLink();
+        return;
+      }
+      if (event.shiftKey && key === "x") {
+        event.preventDefault();
+        insertFormatting("~~", "~~");
+        return;
+      }
+      if (event.shiftKey && (event.key === "`" || event.code === "Backquote")) {
+        event.preventDefault();
+        insertFormatting("`", "`");
+        return;
+      }
+    }
+
     if (event.key !== "Enter") {
       return;
     }