[FEATURE] Add integration for other IP geolocation providers (ipstack alternatives)

[inspiredearth]

Is your feature request related to a problem? Please describe.
The "problem" is that IPStack is relatively expensive. They have a pretty minimal free option (5,000 requests / month). There are other providers with significantly better free and paid options for IP look-ups.

Describe the solution you'd like
I would like to be able to use alternatives to IPStack.

Describe alternatives you've considered
IPINFO — https://ipinfo.io/ — Free plan includes 50,000 look-ups. (Paid plans don't offer any improvement on IPStack).

IPAPI — https://ipapi.co/ — Free plans includes 30,000 look-ips. Paid plan is cheaper than IPStack.

IP Geolocation API — A solution I just discovered. Looks like it might be totally free, and your plugin can make requests to it without any need for site owner to obtain API keys, etc.. https://ipgeolocationapi.com/

https://www.abstractapi.com/ip-geolocation-api — 20k on free plan, and much cheaper than IPSTACK for paid plans.

CONCLUSION — AbstractAPI is best option for paid plans. and IPINFO is the best option for free plan.
I realise you make a commission on people signing up for IPSTACK accounts via your links in the plug-in. So perhaps the motivation to offer other options isn't high. It would, however, be great to have these options.

Thanks very much for your time, and for developing this plugin.

[bmarshall511]

@inspiredearth IPinfo integration will be included in the next release (5.1.1) See #270

[bmarshall511]

@inspiredearth v5.1.1 was just released and includes IPinfo integration.

Hopefully, that helps you out a bit. If you've got time, could you rate the plugin: https://wordpress.org/plugins/zero-spam/ I'd really appreciate it!