docs/ide-support.md: Clarify that clangd replaces IntelliSense
Explain that clangd is not compatible with IntelliSense.
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@@ -69,6 +69,14 @@ ChromeOS source files.
Support for `platform/ec` is not available out of the box (yet), but can be
manually enabled following these steps.
+<!-- mdformat off(b/139308852) -->
+*** note
+NOTE: CrOS IDE uses the VSCode extension `clangd` for code completion and
+navigation. The installation of CrOS IDE disables the built-in
+`C/C++ IntelliSense` because it is not compatible with `clangd`.
+***
+<!-- mdformat on -->
+
### Prerequisites
1. Install CrOS IDE following the [quickstart guide]
