📝 CONTRIBUTING.md; Add syntax for icons

CONTRIBUTING.md

@@ -13,21 +13,21 @@ The following is a set of guidelines for contributing to SLSA-provenance-action,
 - Limit the first line to 72 characters or less
 - Reference issues and pull requests liberally after the first line
 - Consider starting the commit message with an applicable emoji:
-  - :art: when improving the format/structure of the code
-  - :racehorse: when improving performance
-  - :non-potable_water: when plugging memory leaks
-  - :memo: when writing docs
-  - :penguin: when fixing something on Linux
-  - :apple: when fixing something on macOS
-  - :checkered_flag: when fixing something on Windows
-  - :bug: when fixing a bug
-  - :fire: when removing code or files
-  - :green_heart: when fixing the CI build
-  - :white_check_mark: when adding tests
-  - :lock: when dealing with security
-  - :arrow_up: when upgrading dependencies
-  - :arrow_down: when downgrading dependencies
-  - :shirt: when removing linter warnings
+  - :art: `:art:` when improving the format/structure of the code
+  - :racehorse: `:racehorse:` when improving performance
+  - :non-potable_water: `:non-potable_water:` when plugging memory leaks
+  - :memo: `:memo:` when writing docs
+  - :penguin: `:penguin:` when fixing something on Linux
+  - :apple: `:apple:` when fixing something on macOS
+  - :checkered_flag: `:checkered_flag:` when fixing something on Windows
+  - :bug: `:bug:` when fixing a bug
+  - :fire: `:fire:` when removing code or files
+  - :green_heart: `:green_heart:` when fixing the CI build
+  - :white_check_mark: `:white_check_mark:` when adding tests
+  - :lock: `:lock:` when dealing with security
+  - :arrow_up: `:arrow_up:` when upgrading dependencies
+  - :arrow_down: `:arrow_down:` when downgrading dependencies
+  - :shirt: `:shirt:` when removing linter warnings
 
 ### Code