feat: add case-sensitive notice for configuration (#3380)

Co-authored-by: Fabian-Lars <[email protected]>

Author: AprilNEA

src/content/docs/develop/configuration-files.mdx

@@ -76,7 +76,7 @@ pubkey = "updater pub key"
 endpoints = ["https://my.app.updater/{{target}}/{{current_version}}"]
 ```
 
-Note that JSON5 and TOML supports comments, and TOML can use kebab-case for config names which are more idiomatic.
+Note that JSON5 and TOML supports comments, and TOML can use kebab-case for config names which are more idiomatic. Field names are case-sensitive in all 3 formats.
 
 ### Platform-specific Configuration