Ability to cache subsonic artist images locally on disk (#61)

package.json

@@ -8,6 +8,7 @@
   "dependencies": {
     "@svrooij/sonos": "^2.4.0",
     "@types/express": "^4.17.13",
+    "@types/fs-extra": "^9.0.13",
     "@types/morgan": "^1.9.3",
     "@types/node": "^16.7.13",
     "@types/sharp": "^0.28.6",
@@ -18,6 +19,7 @@
     "eta": "^1.12.3",
     "express": "^4.17.1",
     "fp-ts": "^2.11.1",
+    "fs-extra": "^10.0.0",
     "libxmljs2": "^0.28.0",
     "morgan": "^1.10.0",
     "node-html-parser": "^4.1.4",
@@ -35,12 +37,14 @@
     "@types/jest": "^27.0.1",
     "@types/mocha": "^9.0.0",
     "@types/supertest": "^2.0.11",
+    "@types/tmp": "^0.2.1",
     "chai": "^4.3.4",
     "get-port": "^5.1.1",
     "image-js": "^0.33.0",
     "jest": "^27.1.0",
     "nodemon": "^2.0.12",
     "supertest": "^6.1.6",
+    "tmp": "^0.2.1",
     "ts-jest": "^27.0.5",
     "ts-mockito": "^2.6.1",
     "ts-node": "^10.2.1",