Promise API needs TS types

[CodingDoug]

import LibsqlP from 'libsql-experimental/promise'

src/both.ts:3:21 - error TS7016: Could not find a declaration file for module 'libsql-experimental/promise'. 'path/to/node_modules/libsql-experimental/promise.js' implicitly has an 'any' type.
  If the 'libsql-experimental' package actually exposes this module, try adding a new declaration (.d.ts) file containing `declare module 'libsql-experimental/promise';`