Support of http proxy in option

[KeanuPang]

In node-fetch, we can pass a http.Agent with custom proxy settings in options with node-https-proxy-agent.

So maybe we can set http/https proxy settings in option from NotifmeSdk or read from environment variables like http_proxy and https_proxy, then all providers just read this option and pass it to node-fetch.

ref:
node-fetch/node-fetch#79
node-fetch/node-fetch#195

[BDav24]

Ok, I'll look into it.

[BDav24]

@KeanuPang You can now pass a NOTIFME_HTTP_PROXY env variable. If it's set, it'll create a node-https-proxy-agent.

#34
https://github.com/notifme/notifme-sdk/releases/tag/v1.6.0

[KeanuPang]

It's great works, I love this library notifme. Thank you.

[BDav24]

@KeanuPang
Thanks, I'm glad to hear that.
If I may ask, could you tell me how you use this lib? (context, providers...) It's useful to know in order to improve it ;)