URLs in docs are case sensitive (#3750)

Fixing 404 not found

docs/_sidebar.md

@@ -3,7 +3,7 @@
   - [Installing](/docs/Installing)
   - [Working Locally](/docs/WorkingLocally)
   - [Usage](/docs/Usage)
-  - [Showcases](/docs/Showcases)
+  - [Showcases](/docs/showcases)
 - Guide
   - [Top Level](/docs/top-level-api)
   - [Screen](/docs/screen-api)
@@ -16,4 +16,4 @@
 - Migration from v1
   - [Top Level](/docs/top-level-api-migration)
   - [Options](/docs/options-migration)
-- [API](/api/README)
+- [API](/api/README)