Clean up changelog (#10825)

* Clean up changelog

- Forward port entries from 3.1.x branch
- Add note about publish failure in 4.0.0a2 release

* Update CHANGELOG.md

CHANGELOG.md

@@ -38,6 +38,8 @@ github_url: 'https://github.com/jupyterlab/jupyterlab/blob/master/CHANGELOG.md'
 
 ([Full Changelog](https://github.com/jupyterlab/jupyterlab/compare/v4.0.0a1...132f74afab92fb6ca063644951464811d8ae87ae))
 
+**_NOTE_** The Python Package for this release was not published due to our trove classifiers not yet being [available](https://github.com/jupyterlab/jupyterlab/issues/9538#issuecomment-897073510).
+
 ### Bugs fixed
 
 - Share nbformat and nbformatMinor [#10795](https://github.com/jupyterlab/jupyterlab/pull/10795) ([@hbcarlos](https://github.com/hbcarlos))
@@ -113,6 +115,41 @@ github_url: 'https://github.com/jupyterlab/jupyterlab/blob/master/CHANGELOG.md'
 
 ## v3.1
 
+## 3.1.6
+
+([Full Changelog](https://github.com/jupyterlab/jupyterlab/compare/v3.1.5...4cec12eba17eaf313241b595e98b40cb0a851e65))
+
+### Bugs fixed
+
+- Backport PR #10738 on branch 3.1.x [#10806](https://github.com/jupyterlab/jupyterlab/pull/10806) ([@krassowski](https://github.com/krassowski))
+- Share nbformat and nbformatMinor [#10795](https://github.com/jupyterlab/jupyterlab/pull/10795) ([@hbcarlos](https://github.com/hbcarlos))
+- Support collapsible headers with virtual notebook rendering [#10793](https://github.com/jupyterlab/jupyterlab/pull/10793) ([@echarles](https://github.com/echarles))
+
+### Maintenance and upkeep improvements
+
+- Clean up Link Caching Again [#10794](https://github.com/jupyterlab/jupyterlab/pull/10794) ([@afshin](https://github.com/afshin))
+
+### Contributors to this release
+
+([GitHub contributors page for this release](https://github.com/jupyterlab/jupyterlab/graphs/contributors?from=2021-08-09&to=2021-08-12&type=c))
+
+[@blink1073](https://github.com/search?q=repo%3Ajupyterlab%2Fjupyterlab+involves%3Ablink1073+updated%3A2021-08-09..2021-08-12&type=Issues) | [@jupyterlab-dev-mode](https://github.com/search?q=repo%3Ajupyterlab%2Fjupyterlab+involves%3Ajupyterlab-dev-mode+updated%3A2021-08-09..2021-08-12&type=Issues) | [@krassowski](https://github.com/search?q=repo%3Ajupyterlab%2Fjupyterlab+involves%3Akrassowski+updated%3A2021-08-09..2021-08-12&type=Issues) | [@meeseeksmachine](https://github.com/search?q=repo%3Ajupyterlab%2Fjupyterlab+involves%3Ameeseeksmachine+updated%3A2021-08-09..2021-08-12&type=Issues)
+
+## 3.1.5
+
+([Full Changelog](https://github.com/jupyterlab/jupyterlab/compare/v3.1.4...6d14f7f8d3a7400a5fddbbdfaf79d0b8bdd5325f))
+
+### Bugs fixed
+
+- Revert input guard [#10779](https://github.com/jupyterlab/jupyterlab/pull/10779) ([@echarles](https://github.com/echarles))
+- Markdown url resolver no longer throws for malformed URLs in `isLocal` check [#10773](https://github.com/jupyterlab/jupyterlab/pull/10773) ([@loichuder](https://github.com/loichuder))
+
+### Contributors to this release
+
+([GitHub contributors page for this release](https://github.com/jupyterlab/jupyterlab/graphs/contributors?from=2021-08-05&to=2021-08-09&type=c))
+
+[@echarles](https://github.com/search?q=repo%3Ajupyterlab%2Fjupyterlab+involves%3Aecharles+updated%3A2021-08-05..2021-08-09&type=Issues) | [@jupyterlab-dev-mode](https://github.com/search?q=repo%3Ajupyterlab%2Fjupyterlab+involves%3Ajupyterlab-dev-mode+updated%3A2021-08-05..2021-08-09&type=Issues) | [@meeseeksmachine](https://github.com/search?q=repo%3Ajupyterlab%2Fjupyterlab+involves%3Ameeseeksmachine+updated%3A2021-08-05..2021-08-09&type=Issues) | [@welcome](https://github.com/search?q=repo%3Ajupyterlab%2Fjupyterlab+involves%3Awelcome+updated%3A2021-08-05..2021-08-09&type=Issues)
+
 ## 3.1.2
 
 ([Full Changelog](https://github.com/jupyterlab/jupyterlab/compare/v3.1.1...be8032d1a932e09f553d0343659e89a6a25a516f))