Added some description of the Makefile in the contributing.md

Signed-off-by: Yash Sharma <yashrsharma44@gmail.com>

CONTRIBUTING.md

@@ -7,8 +7,19 @@ Fork, then clone the repo:
 ```bash
 git clone git@github.com:your-username/go-grpc-middleware.git
 ```    
+Before submitting a patch, please make sure to run the following make commands for running checks - 
+Make commands for running formatting/tests/generate proto files/vetting
+```powershell
+make fmt : Run formatting across all go files
 
-Before checking in please run the following:
+make proto : Generate proto files
+
+make test : Run all the tests
+
+make vet : Run vetting across all go files
+```
+
+One command to rule them all:
 
 ```bash
 make all