Bump @types/socket.io from 2.1.11 to 2.1.12 in /backend

Bumps [@types/socket.io](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/socket.io) from 2.1.11 to 2.1.12.
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/socket.io)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

backend/package.json

@@ -14,7 +14,7 @@
   },
   "devDependencies": {
     "@types/lodash": "4.14.165",
-    "@types/socket.io": "^2.1.11",
+    "@types/socket.io": "^2.1.12",
     "@types/uuid": "^7.0.0",
     "ts-node-dev": "^1.0.0-pre.60",
     "ts-node": "^9.0.0",

backend/yarn.lock

@@ -19,13 +19,21 @@
   resolved "https://registry.yarnpkg.com/@types/node/-/node-13.9.0.tgz#5b6ee7a77faacddd7de719017d0bc12f52f81589"
   integrity sha512-0ARSQootUG1RljH2HncpsY2TJBfGQIKOOi7kxzUY6z54ePu/ZD+wJA8zI2Q6v8rol2qpG/rvqsReco8zNMPvhQ==
 
-"@types/socket.io@^2.1.11":
-  version "2.1.11"
-  resolved "https://registry.yarnpkg.com/@types/socket.io/-/socket.io-2.1.11.tgz#e0d6759880e5f9818d5297a3328b36641bae996b"
-  integrity sha512-bVprmqPhJMLb9ZCm8g0Xy8kwBFRbnanOWSxzWkDkkIwxTvud5tKMfAJymXX6LQbizUKCS1yima7JM4BeLqjNqA==
+"@types/socket.io-parser@*":
+  version "2.2.1"
+  resolved "https://registry.yarnpkg.com/@types/socket.io-parser/-/socket.io-parser-2.2.1.tgz#dc94aed303839487f4975249a32a548109ea3647"
+  integrity sha512-+JNb+7N7tSINyXPxAJb62+NcpC1x/fPn7z818W4xeNCdPTp6VsO/X8fCsg6+ug4a56m1v9sEiTIIUKVupcHOFQ==
+  dependencies:
+    "@types/node" "*"
+
+"@types/socket.io@^2.1.12":
+  version "2.1.12"
+  resolved "https://registry.yarnpkg.com/@types/socket.io/-/socket.io-2.1.12.tgz#91187f826a5dd2ed1113e935815bbaf9627e5cb0"
+  integrity sha512-oStc5VFkpb0AsjOxQUj9ztX5Iziatyla/rjZTYbFGoVrrKwd+JU2mtxk7iSl5RGYx9WunLo6UXW1fBzQok/ZyA==
   dependencies:
     "@types/engine.io" "*"
     "@types/node" "*"
+    "@types/socket.io-parser" "*"
 
 "@types/strip-bom@^3.0.0":
   version "3.0.0"