add "exports.types" for strict mode TS support

[dilame]

Without this change i get

TS7016: Could not find a declaration file for module 'hpagent'.
'/Users/bowzee/WebstormProjects/trading.bot/node_modules/hpagent/index.mjs' implicitly has an 'any' type.
Try `npm i --save-dev @types/hpagent` if it exists or add a new declaration (.d.ts) file containing `declare module 'hpagent';`

[Maxim-Mazurok]

Can confirm that this closes #95 thanks!

[Maxim-Mazurok]

Would be great if you could edit the description to include closes #95 to link them

[mrl5]

I can confirm that I also experience bug described in #94 and indeed the fix introduced in this PR solves it.

It would be nice to merge and release this oneliner already :D friendly ping @delvedor

thanks @Maxim-Mazurok for reporting and @dilame for fixing!