Add Corso known issues (#1235)

## Description

Add Corso known issues

## Type of change

<!--- Please check the type of change your PR introduces: --->
- [ ] 🌻 Feature
- [ ] 🐛 Bugfix
- [x] 🗺️ Documentation
- [ ] 🤖 Test
- [ ] 💻 CI/Deployment
- [ ] 🐹 Trivial/Minor

## Issue(s)
closes #1180
<!-- Can reference multiple issues. Use one of the following "magic words" - "closes, fixes" to auto-close the Github issue. -->

## Test Plan

<!-- How will this be tested prior to merging.-->
- [x] 💪 Manual
- [ ] ⚡ Unit test
- [ ] 💚 E2E

docs/docs/known_issues.md

@@ -0,0 +1,10 @@
+# Known issues
+
+Below is a list of known Corso issues and limitations:
+
+* Only supports Exchange (email, calendars, contact) and OneDrive (files) M365 data. Additional
+  data types and services will be added in subsequent releases.
+
+* Restores are non-destructive to a dedicated restore folder in the original Exchange mailbox or OneDrive account.
+  Advanced restore options such as in-place restore, or restore to a specific folder or to a different account aren't
+  yet supported.

docs/sidebars.js

@@ -45,7 +45,7 @@ const sidebars = {
         'developers/build', 'developers/testing', 'developers/linters'
       ],
     },
-
+    'known_issues',
   ],
 };