Add "Releasing" section for CocoaPods to the ReadMe
From the discussion [here](https://github.com/grpc/grpc-swift/issues/279#issuecomment-412572907).
MODIFY
README.md
README.md
@@ -146,3 +146,14 @@ grpc-swift is released under the same license as
## Contributing
Please get involved! See our [guidelines for contributing](CONTRIBUTING.md).
+
+### Releasing
+
+Prior to creating a new release tag for SwiftGRPC, the `.podspec` file's version should be bumped, and the
+CocoaPods spec linter should be run to ensure that there are no new warnings/errors:
+
+ $ pod spec lint SwiftGRPC.podspec
+
+Once a new release tag is created, the updated CocoaPods spec should also be pushed to the master specs repo:
+
+ $ pod trunk push SwiftGRPC.podspec

Add "Releasing" section for CocoaPods to the ReadMe

From the discussion [here](https://github.com/grpc/grpc-swift/issues/279#issuecomment-412572907).