(DOCSP-30684): Add Bluehawk and Find Unused Files GH actions (#100)

# Pull Request Info

[PR Reviewing
Guidelines](https://github.com/mongodb/docs-java/blob/master/REVIEWING.md)

Add the following GH actions to run on PRs:
- Bluehawk - checks for Bluehawk errors (e.g. bad syntax)
- Find Unused Files - doc doctor check for unused files

JIRA - https://jira.mongodb.org/browse/DOCSP-30684
Staging -
https://docs-mongodbcom-staging.corp.mongodb.com/kotlin/docsworker-xlarge/docsp-30684-gh-actions/

## Self-Review Checklist

- [ ] Is this free of any warnings or errors in the RST?
- [ ] Did you run a spell-check?
- [ ] Did you run a grammar-check?
- [ ] Are all the links working?

Author: cbullinger

.github/workflows/bluehawk.yml

@@ -0,0 +1,14 @@
+name: Bluehawk
+
+on: pull_request
+
+jobs:
+  check:
+    name: Check
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-node@v1
+        with:
+          node-version: 15.x
+      - run: npx bluehawk check -i "*.md" -i "*.properties" -i "*.lock" examples

.github/workflows/find-unused.yml

@@ -0,0 +1,15 @@
+name: Find Unused Files
+
+on:
+  pull_request:
+    paths:
+      - "source/**"
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: cbush/docdoctor/actions/find-unused@main
+        with:
+          source: ./source