Ask ESLint to report floating Promises

This rule is quite helpful in avoiding hard-to-debug missing `await`s.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

.eslintrc.json

@@ -27,6 +27,7 @@
     "@typescript-eslint/no-empty-interface": "error",
     "@typescript-eslint/no-explicit-any": "error",
     "@typescript-eslint/no-extraneous-class": "error",
+    "@typescript-eslint/no-floating-promises": "error",
     "@typescript-eslint/no-for-in-array": "error",
     "@typescript-eslint/no-inferrable-types": "error",
     "@typescript-eslint/no-misused-new": "error",