Merge pull request #5585 from stanley-cheung/update-manifest-md

Doc Fixit: Update MANIFEST.md

MANIFEST.md

 # Top-level Items by language
 
+## Bazel
+* [grpc.bzl](grpc.bzl)
+
 ## Node
 * [binding.gyp](binding.gyp)
+* [package.json](package.json)
 
 ## Objective-C
 * [gRPC.podspec](gRPC.podspec)
 
+## PHP
+* [composer.json](composer.json)
+* [config.m4](config.m4)
+* [package.xml](package.xml)
+
 ## Python
 * [requirements.txt](requirements.txt)
 * [setup.cfg](setup.cfg)
 * [setup.py](setup.py)
 * [tox.ini](tox.ini)
 * [PYTHON-MANIFEST.in](PYTHON-MANIFEST.in)
+
+## Ruby
+* [Gemfile](Gemfile)
+* [grpc.gemspec](grpc.gemspec)
+* [Rakefile](Rakefile)