Merge branch 'main' into glitch-soc/merge-upstream

Conflicts:
- `README.md`:
  Upstream added some text, but our README is completely different.
  Kept our README unchanged.

app/javascript/mastodon/actions/compose.js

@@ -254,12 +254,15 @@ export function uploadCompose(files) {
           if (status === 200) {
             dispatch(uploadComposeSuccess(data, f));
           } else if (status === 202) {
+            let tryCount = 1;
             const poll = () => {
               api(getState).get(`/api/v1/media/${data.id}`).then(response => {
                 if (response.status === 200) {
                   dispatch(uploadComposeSuccess(response.data, f));
                 } else if (response.status === 206) {
-                  setTimeout(() => poll(), 1000);
+                  let retryAfter = (Math.log2(tryCount) || 1) * 1000;
+                  tryCount += 1;
+                  setTimeout(() => poll(), retryAfter);
                 }
               }).catch(error => dispatch(uploadComposeFail(error)));
             };