Commence converting Cashtab to typescript by updating 2 simple files, appConfig and formatting. 2 files because `formatting` has functions, which are unit-tested, so we can confirm the implementation does not break jest --- and `formatting` imports `appConfig`. Seemed like the smallest possible change.
Update linters and webpack settings to support ts
Going forward, will be a big process to get Cashtab fully converted. But we can now use typescript for any new developments. It's particularly important for working with agora and chronik-client.