More eslint fixes

Oh oops, my no-unused-vars changes affected more than I realized! It caused builds to break.

I've now fixed it to pass on our existing codebase!

package.json

@@ -89,10 +89,12 @@
         }
       ],
       "import/first": "off",
-      "no-unused-vars": [
+      "no-unused-vars": "off",
+      "@typescript-eslint/no-unused-vars": [
         "warn",
         {
-          "varsIgnorePattern": "^unused"
+          "varsIgnorePattern": "^unused",
+          "argsIgnorePattern": "^_+$|^e$"
         }
       ]
     }
@@ -131,6 +133,7 @@
     "react-is": "^16.13.1",
     "ts-node": "^9.1.1",
     "typescript-cached-transpile": "^0.0.6",
+    "typescript-eslint": "^0.0.1-alpha.0",
     "vercel": "^21.2.3"
   }
 }

yarn.lock

@@ -18429,6 +18429,11 @@ typescript-cached-transpile@^0.0.6:
     fs-extra "^8.1.0"
     tslib "^1.10.0"
 
+typescript-eslint@^0.0.1-alpha.0:
+  version "0.0.1-alpha.0"
+  resolved "https://registry.yarnpkg.com/typescript-eslint/-/typescript-eslint-0.0.1-alpha.0.tgz#285d68a4e96588295cd436278801bcb6a6b916c1"
+  integrity sha512-1hNKM37dAWML/2ltRXupOq2uqcdRQyDFphl+341NTPXFLLLiDhErXx8VtaSLh3xP7SyHZdcCgpt9boYYVb3fQg==
+
 typescript@3.9.3:
   version "3.9.3"
   resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.9.3.tgz#d3ac8883a97c26139e42df5e93eeece33d610b8a"