MVP of Apache Airflow Plugin

Adds support for a new Backstage integration with the Apache Airflow workflow
management platform. This implementation has been tested with Apache Airflow v2
API authenticating with basic auth through the Backstage proxy plugin.

Supported functionality include:
- Information card of version information for the Airflow instance
- Information card of  instance status (health) for metadatabase and scheduler
- Table of DAGs with meta information and status, along with a link to view
  details in the Airflow UI

Signed-off-by: Colton Padden <colton.padden@fastmail.com>

plugins/apache-airflow/package.json

@@ -0,0 +1,52 @@
+{
+  "name": "@backstage/plugin-apache-airflow",
+  "version": "0.0.0",
+  "main": "src/index.ts",
+  "types": "src/index.ts",
+  "license": "Apache-2.0",
+  "publishConfig": {
+    "access": "public",
+    "main": "dist/index.esm.js",
+    "types": "dist/index.d.ts"
+  },
+  "scripts": {
+    "build": "backstage-cli plugin:build",
+    "start": "backstage-cli plugin:serve",
+    "lint": "backstage-cli lint",
+    "test": "backstage-cli test",
+    "diff": "backstage-cli plugin:diff",
+    "prepack": "backstage-cli prepack",
+    "postpack": "backstage-cli postpack",
+    "clean": "backstage-cli clean"
+  },
+  "dependencies": {
+    "@backstage/core-components": "^0.7.4",
+    "@backstage/core-plugin-api": "^0.2.0",
+    "@backstage/theme": "^0.2.13",
+    "@material-ui/core": "^4.12.2",
+    "@material-ui/icons": "^4.9.1",
+    "@material-ui/lab": "4.0.0-alpha.57",
+    "cross-fetch": "^3.0.6",
+    "qs": "^6.10.1",
+    "react": "^16.13.1",
+    "react-dom": "^16.13.1",
+    "react-use": "^17.2.4"
+  },
+  "devDependencies": {
+    "@backstage/cli": "^0.9.0",
+    "@backstage/core-app-api": "^0.1.22",
+    "@backstage/dev-utils": "^0.2.13",
+    "@backstage/test-utils": "^0.1.22",
+    "@testing-library/jest-dom": "^5.10.1",
+    "@testing-library/react": "^11.2.5",
+    "@testing-library/user-event": "^13.1.8",
+    "@types/jest": "*",
+    "@types/node": "*",
+    "msw": "^0.35.0"
+  },
+  "files": [
+    "dist",
+    "config.d.ts"
+  ],
+  "configSchema": "config.d.ts"
+}