feat(proxy): add proxy

[mar-heaven]

set proxy from env

[foamzou]

Thanks the PR. Could you help to add the proxy for all the request? Such as the function createClient().
Your PR would be serve when the default environment proxy was set.

And I have a idea that media-get can provide the options to let the user set diffrent proxy per website/source.
For example. I would like to set the a proxy for youtube and set the b proxy for douyin.
I need to make a friendly options design for the feature. Both of the following is need.

1. default config file for media-get. Place to /$HOME/.media-get.json
2. cmd options

Not just for the user, after the feature launched, the CI would be run well 😄

[mar-heaven]

Good idea! i'm going to enhance the feature.

[foamzou]

The feature has been implemented by #12

Thx for your working anyway, bro.

Closed the PR.