No support for PRO subscription

[morph-dev]

note: I'm aware that there is #13 but that one is closed and I wanted to start new discussion.

The PRO subscription request has to (source):

• go to separate url: https://pro-api.coingecko.com/api/v3/
• pro_api_key has to be included, either as request header x-cg-pro-api-key or request param x_cg_pro_api_key

I'm willing to make a PR for it.

Proposed approach:

• add optional pro_api_key to constructor
• If pro_api_key is set and non-empty:
  • change request endpoint
  • add x-cg-pro-api-key header

[morph-dev]

It's also worth noting that there are some API-s that are available only to PRO subscribers, but I don't plan to add those (at least not initially).

[0xMobeus]

Support for api keys will be great.

[morph-dev]

I can make the PR. I even have api key that I can use to test and verify that it works.

[cysedhu]

@morph-dev : do u have any fork ? i also want pro api support and i can also contribute !!

[samuraitruong]

@cysedhu I think this already merged with this PR https://github.com/samuraitruong/coingecko-api-v3/pull/31