Create type definitions

[ciatph]

Is your feature request related to a problem? Please describe.

• Need for better support and tooling for TypeScript users by defining the expected types (shape) definitions of the (CommonJS) class and function input parameters and output.

Describe the solution you'd like

• Create .d.ts files containing function, class, and global type definitions used by the ph-municipalities classes and functions.
• Include the .d.ts files in the npm package.

Describe alternatives you've considered

• Writing JSDoc annotations about the functions and their input/output function parameters
• Sometimes, these are verbose and do not capture the actual shape and type of the input/output function parameters