Added function parameter types, return type, and types of local
varaibles. Added a `null` check for `raw_data` before `JSON.parse`.
Created a type `FormData` and an export type `LocalStorage` to
imporve conciseness and clearity.
Type `LocalStorage` is exported because it might be used in other
files based on an observation that many files have imported `localstorage`.
This directory contains scripts that are used in building, managing,
testing, and other forms of work in a Zulip development environment.
Note that tools that are also useful in production belong in
scripts/ or should be Django management commands.