Fix geohash for neighbours and removed deprecated curly braces

• Neighbors are calculated incorrectly for some geohashes whenever last character is empty.
• Removed usage of curly braces as its deprecated in php 7.4.

Neighbor geohashes

Geohash library now supports identifying neighbouring geohashes for the provided geohash.

v0.9

Supports both encoding and decoding. Added php unit tests.

Pre release version of this library

• It is in still development phase.
• It supports encoding and decoding functions.
• Php unit tests and stable documentation will be out soon