Allow multi file support for extensions

[Moros1138]

Added multi file support for the extensions by adding #include "olcPixelGameEngine.h" to headers that was missing it.

At the same time, olcPGEX_Graphics3D produces the following errors

In file included from ./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.cpp:2:
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:209:138: error: default member initializer for 'w' needed within definition of enclosing class 'GFX3D' outside of member functions
  209 |                         void SetLightSource(uint32_t nSlot, uint32_t nType, olc::Pixel col, olc::GFX3D::vec3d pos, olc::GFX3D::vec3d dir = { 0.0f, 0.0f, 1.0f }, float fParam = 0.0f);
      |                                                                                                                                                               ^
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:105:10: note: default member initializer declared here
  105 |                         float w = 1; // Need a 4th term to perform sensible matrix vector multiplication
      |                               ^
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:595:18: error: no viable overloaded '='
  595 |                         out_tri1.p[0] = *inside_points[0];
      |                         ~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:100:10: note: candidate function (the implicit move assignment operator) not viable: expects an rvalue for 1st argument
  100 |                 struct vec3d
      |                        ^~~~~
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:631:18: error: no viable overloaded '='
  631 |                         out_tri1.p[0] = *inside_points[0];                      
      |                         ~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:100:10: note: candidate function (the implicit move assignment operator) not viable: expects an rvalue for 1st argument
  100 |                 struct vec3d
      |                        ^~~~~
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:634:18: error: no viable overloaded '='
  634 |                         out_tri1.p[1] = *inside_points[1];
      |                         ~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:100:10: note: candidate function (the implicit move assignment operator) not viable: expects an rvalue for 1st argument
  100 |                 struct vec3d
      |                        ^~~~~
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:646:18: error: no viable overloaded '='
  646 |                         out_tri2.p[1] = *inside_points[1];
      |                         ~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:100:10: note: candidate function (the implicit move assignment operator) not viable: expects an rvalue for 1st argument
  100 |                 struct vec3d
      |                        ^~~~~
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:648:18: error: no viable overloaded '='
  648 |                         out_tri2.p[0] = out_tri1.p[2];
      |                         ~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:100:10: note: candidate function (the implicit move assignment operator) not viable: expects an rvalue for 1st argument
  100 |                 struct vec3d
      |                        ^~~~~
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:1018:22: error: no viable overloaded '='
 1018 |                         lights[nSlot].pos = pos;
      |                         ~~~~~~~~~~~~~~~~~ ^ ~~~
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:100:10: note: candidate function (the implicit move assignment operator) not viable: expects an rvalue for 1st argument
  100 |                 struct vec3d
      |                        ^~~~~
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:1019:22: error: no viable overloaded '='
 1019 |                         lights[nSlot].dir = dir;
      |                         ~~~~~~~~~~~~~~~~~ ^ ~~~
./include/olcPixelGameEngine/extensions/olcPGEX_Graphics3D.h:100:10: note: candidate function (the implicit move assignment operator) not viable: expects an rvalue for 1st argument
  100 |                 struct vec3d
      |                        ^~~~~
8 errors generated.

Which was fixed by adding the 4th term to the initializer list, default value for w