Add ip2geo IP geolocation provider

[bfzli]

Summary

• Adds a new provider for the ip2geo IP geolocation API
• Supports IPv4 and IPv6 address geocoding
• Returns 30+ fields: city, country, continent, ASN, currency, flag, timezone, etc.
• API key authentication via X-Api-Key header

Usage

import geocoder

g = geocoder.ip2geo('8.8.8.8', key='your-api-key')
print(g.city)       # Los Angeles
print(g.latlng)     # [34.0544, -118.244]
print(g.org)        # Los Angeles Department Of Water & Power
print(g.timezone)   # America/Los_Angeles

Files changed

• New: geocoder/ip2geo.py — provider module (Ip2geoQuery + Ip2geoResult)
• New: tests/test_ip2geo.py — basic test
• Modified: geocoder/api.py — register provider in options dict + convenience function
• Modified: geocoder/__init__.py — export ip2geo function

Test plan

• Provider loads and registers correctly via geocoder.ip2geo()
• All result properties map correctly from API response
• Live API test with real key returns correct data