ci(java): suggest formatting fixes

GitHub action config to run the java formatter and suggest inline fixes on the pull request.

This was tested in java-asset: [example PR](#392).

Source-Author: Jeff Ching <chingor@google.com>
Source-Date: Tue Oct 13 09:04:08 2020 -0700
Source-Repo: googleapis/synthtool
Source-Sha: b65ef07d99946d23e900ef2cc490274a16edd336
Source-Link: googleapis/synthtool@b65ef07

.github/workflows/formatting.yaml

@@ -18,7 +18,7 @@ jobs:
         with:
           java-version: 11
       - run: "mvn com.coveo:fmt-maven-plugin:format"
-      - uses: googleapis/code-suggester@v1.8.0 # takes the changes from git directory
+      - uses: googleapis/code-suggester@v1.8.0
         with:
           command: review
           pull_number: ${{ github.event.pull_request.number }}

synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-asset.git",
-        "sha": "003e7019a6775ee68ffd1ed169ed12bee3ba4448"
+        "sha": "52914a81247ea37afdd2bb8939f019559af28c08"
       }
     },
     {
@@ -59,7 +59,7 @@
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "0762e8ee2ec21cdfc4d82020b985a104feb0453b"
+        "sha": "b65ef07d99946d23e900ef2cc490274a16edd336"
       }
     }
   ],
@@ -130,6 +130,7 @@
     ".github/trusted-contribution.yml",
     ".github/workflows/auto-release.yaml",
     ".github/workflows/ci.yaml",
+    ".github/workflows/formatting.yaml",
     ".github/workflows/samples.yaml",
     ".kokoro/build.bat",
     ".kokoro/build.sh",