Docs: Add required Cargo version to install guide (#191)

diff --git a/website/src/install.md b/website/src/install.md
index 3a96cb5..38b76a9 100644
--- a/website/src/install.md
+++ b/website/src/install.md
@@ -19,6 +19,10 @@
 
 # Install
 
+<div class="warning">
+Cargo 1.75.0 or later is required to build.
+</div>
+
 Add `iceberg` into `Cargo.toml` dependencies:
 
 ```toml