Explicative section in the README about `Ord` and `PartialOrd`

# Work done

Added a storage optimized `HexagonalMap` utilizing some tricks to be
able to store hex maps in a 2d vector instead on having to rely on
hashmaps.

> See https://www.redblobgames.com/grids/hexagons/#map-storage

## Usage

This implementation only supports:
- **Dense**
- Hexagon-shaped
- Fixed sized

storage.

This can be useful for large hexagon shaped maps, as well as for chunk
based maps, chunking would usually be of hexagonal shape.

## TODO

- [x] Benchmark
- [x] Usage in an example
- [x] Changelog

Follow up to #163 

Added 1D optimized storage for rombus shapes

- Hex ring +50%
- Hex corner wedge + 50%

- New shapes explorer example
- New shape builder structs

Added `Hex::rectiline_to` 

## Misc changes

* Added `HexLayout::all_edges_cordinates` 
* Added `DirectionWay::map` 

## Cleanup for 0.17 

* (**BREAKING**) Removed the following ambiguous const values: 
  * `Hex::Z`
  * `Hex::NEG_Z`
  * `Hex::AXES`
  * `Hex::AXES`