add basic docs

Author: bend-n

compiler/rustc_lint_defs/src/builtin.rs

@@ -4952,7 +4952,22 @@ declare_lint! {
 }
 
 declare_lint! {
-    /// Wow such docs.
+    /// The `redundant_transmutation` lint detects transmutations that have safer alternatives.
+    ///
+    /// ### Example
+    ///
+    /// ```
+    /// fn bytes_at_home(x: [u8; 4]) -> u32 {
+    ///   transmute(x)
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ## Explanation
+    ///
+    /// People dont realize that safer methods such as [`u32::to_ne_bytes`] exist,
+    /// so this lint exists to lint on cases where people write transmutes that dont need to be there.
     pub REDUNDANT_TRANSMUTATION,
     Warn,
     "detects transmutes that are shadowed by std methods"