TS1046
Top-level declarations in .d.ts files must start with either a 'declare' or 'export' modifier.
Declaration files (.d.ts) cannot contain implementation code, they can only
describe the shape of a module. Therefore the following will cause this error:
const a = 1;Fix: Add 'declare' or 'export' to each top-level declaration.
Ensure each top-level declaration uses the declare or export keyword:
declare const a: 1;