structure du projet, ajout de la lib hexagonal

Src/HexagonalLib/README.md

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+# HexagonalLib implementation for .NET
+ 
+_I was highly inspired by this article: [https://www.redblobgames.com/grids/hexagons/](https://www.redblobgames.com/grids/hexagons/) and this repo is mostly just C# implementation of it. Recommended for reading. Here I will describe some technical details regarding implementation._
+ 
+## Hexagonal grid
+ 
+To use hexagonal grids you need to create [HexagonalGrid](src/HexagonalLib/HexagonalGrid.cs) and initialize it with grid type and inscribed radius of hex. 
+ 
+```C#
+var grid = new HexagonalGrid(HexagonalGridType.PointyEven, 1.0f);
+```
+ 
+Grids layouts and orientations are merged to one enum [HexagonalGridType](src/HexagonalLib/HexagonalGridType.cs).
+ 
+*   PointyOdd - Horizontal layout shoves odd rows right [odd-r]
+*   PointyEven - Horizontal layout shoves even rows right [even-r]
+*   FlatOdd - Vertical layout shoves odd columns down [odd-q]
+*   FlatEven - Vertical layout shoves even columns down [even-q]
+ 
+ 
+## Coordinates systems
+ 
+There is three coordinates systems represented in lib:
+ 
+*   [Offset](src/HexagonalLib/Coordinates/Offset.cs) - offset coordinates ([link](https://www.redblobgames.com/grids/hexagons/#coordinates-offset))
+*   [Cubic](src/HexagonalLib/Coordinates/Cubic.cs) - cube coordinates ([link](https://www.redblobgames.com/grids/hexagons/#coordinates-cube))
+*   [Axial](src/HexagonalLib/Coordinates/Axial.cs) -  axial coordinates ([link](https://www.redblobgames.com/grids/hexagons/#coordinates-axial))
+ 
+_Note: there is no [Doubled](https://www.redblobgames.com/grids/hexagons/#coordinates-doubled) coordinates yet. I will add them in later versions._
+ 
+ 
+Struct [HexagonalGrid](src/HexagonalLib/HexagonalGrid.cs) contains a bunch of methods for coordinates conversion (all details are [described](https://www.redblobgames.com/grids/hexagons/#conversions) in original article):
+ 
+```C#
+var offsetFromCubic = grid.ToOffset(cubic);
+var offsetFromAxial = grid.ToOffset(axial);
+ 
+var cubicFromOffset = grid.ToCubic(offset);
+var cubicFromAxial = grid.ToCubic(axial);
+ 
+var axialFromOffset = grid.ToAxial(offset);
+var axialFromCubic = grid.ToAxial(cubic);
+```
+
+## Neighbors
+ 
+There is the order of neighbors of hex:
+ 
+![](img/hex-neighbors-order.png)
+ 
+You can take a neighbor of any hex by providing a coordinate of hex and required neighbor index. 
+ 
+```C#
+var oNeighbor = grid.GetNeighbor(offset, neighborIndex);
+var cNeighbor = grid.GetNeighbor(cubic, neighborIndex);
+var aNeighbor = grid.GetNeighbor(axial, neighborIndex);
+```
+_The neighbor index can be negative or greater than 5 (it will be normalized)_
+
+Or you can take all neighbors of particular hex
+
+```C#
+var oNeighbors = grid.GetNeighbors(offset);
+var cNeighbors = grid.GetNeighbors(cubic);
+var aNeighbors = grid.GetNeighbors(axial);
+```
+ 
+There is also option to check are two hexes neighbors or not:
+ 
+```C#
+var isNeighbors1 = grid.IsNeighbors(offset, oNeighbor);
+var isNeighbors2 = grid.IsNeighbors(cubic, cNeighbor);
+var isNeighbors3 = grid.IsNeighbors(axial, aNeighbor);
+```
+
+### Ring of neighbors
+You also can get ring of neighbor for particular hex
+
+![](img/hex-rings.png)
+
+```C#
+var oNeighbors = grid.GetNeighborsRing(offset, radius);
+var cNeighbors = grid.GetNeighborsRing(cubic, radius);
+var aNeighbors = grid.GetNeighborsRing(axial, radius);
+```
+
+### Circle of neighbors
+Same as ring but you will receive hexes from all rings
+
+![](img/hex-around.png)
+
+```C#
+var oNeighbors = grid.GetNeighborsAround(offset, radius);
+var cNeighbors = grid.GetNeighborsAround(cubic, radius);
+var aNeighbors = grid.GetNeighborsAround(axial, radius);
+```
+
+## 2D space 
+
+There is also list of methods to convert hex coordinate to its center (point represented as tuple):
+ 
+```C#
+var pointFromOffset = grid.ToPoint2(offset);
+var pointFromCubic = grid.ToPoint2(cubic);
+var pointFromAxial = grid.ToPoint2(axial);
+```
+ 
+To convert point into a hex coordinate which contains this point you can use:
+ 
+```C#
+var offsetFromPoint = grid.ToOffset(x, y);
+var cubicFromPoint = grid.ToCubic(x, y);
+var axialFromPoint = grid.ToAxial(x, y);
+```
+ 
+Hexagons have 6 sides and 6 corners. There is corners order of the hexes:
+
+![](img/hex-corners-order.png)
+
+To take them in code simly use:
+
+```C#
+var cornerFromOffset = grid.GetCorner(offset, cornerIndex);
+var cornerFromCubic = grid.GetCorner(cubic, cornerIndex);
+var cornerFromAxial = grid.GetCorner(axial, cornerIndex);
+```
+_The corner index can be negative or greater than 5 (it will be normalized)_