chore: show Cargo.lock as a non-generated file

This causes GitHub's PR review view to display changes to this file by default, as it is highly important and worth visually inspecting changes.

Signed-off-by: Shane Utt <[email protected]>

Author: shaneutt

.gitattributes

@@ -2,3 +2,4 @@ bin/** linguist-detectable=false
 config/** linguist-detectable=false
 test/** linguist-detectable=false
 tools/** linguist-detectable=false
+Cargo.lock linguist-generated=false