Add lint rule for unhandled promise rejections

.eslintrc.json

@@ -21,6 +21,7 @@
     "@typescript-eslint/no-explicit-any": 0,
     "@typescript-eslint/no-use-before-define": ["error", { "functions": false }],
     "@typescript-eslint/explicit-function-return-type": ["error", { "allowExpressions": true }],
+    "@typescript-eslint/no-floating-promises": "error",
     "require-atomic-updates": 0,
     "no-prototype-builtins": 0
   }