We turn off the eslint no-use-before-define for TypeScript files
because it does not work correctly for types. There is already
a typescript-eslint version of it that is enabled for TS.
We also update the error handler on window to use instanceof check
for ErrorEvent instead of checking the error property.
The plan for type annotating the page_params is to set it to
Record<string, unknown> for now and then annotate individual
properties on it as we use it in typescript modules.
Priyank Patel