basic PBR example (#3621)

* basic pbr example

pbr implementation  includes rpbr.h and few shader files header only file, which self contain everything needed for pbr rendering. Few textures and one model of the car which is under free licence which is included inside basic_pbr.c example file  currently supported shader versions are 120 and 330 , version 100 has small issue which I have to resolve

* Unloading PBRMAterial

I forgot unloading PBRMaterial

* fix small issue with texOffset assigment.

value was Vector4 at first but I found out it would be unclear for and users, so I change to have two Vector2 instead, but forgot to assign offset .

* Changed size of textures and file name changed

Changed size of textures from 2048x2048 to 1024x1024 and file name changed to shaders_basic_pbr.c ,
Added the function PBRModel PBRModelLoadFromMesh(Mesh mesh);
but GenMeshPlane(2, 2.0, 3, 3) culdn't be used because it crash once GenMeshTangents() is used with that plane mesh

examples/shaders/resources/shaders/glsl330/pbr.vs

@@ -0,0 +1,49 @@
+#version 330
+
+// Input vertex attributes
+in vec3 vertexPosition;
+in vec2 vertexTexCoord;
+in vec3 vertexNormal;
+in vec3 vertexTangent;
+in vec4 vertexColor;
+
+// Input uniform values
+uniform mat4 mvp;
+uniform mat4 matModel;
+uniform mat4 matNormal;
+uniform vec3 lightPos;
+uniform vec4 difColor;
+
+// Output vertex attributes (to fragment shader)
+out vec3 fragPosition;
+out vec2 fragTexCoord;
+out vec4 fragColor;
+out vec3 fragNormal;
+out mat3 TBN;
+
+const float normalOffset = 0.1;
+
+void main()
+{
+
+    // calc binormal from vertex normal and tangent
+    vec3 vertexBinormal = cross(vertexNormal, vertexTangent);
+    // calc fragment normal based on normal transformations
+    mat3 normalMatrix = transpose(inverse(mat3(matModel)));
+    // calc fragment position based on model transformations
+
+    fragPosition = vec3(matModel*vec4(vertexPosition, 1.0f));
+
+    fragTexCoord = vertexTexCoord*2.0;
+
+    fragNormal = normalize(normalMatrix*vertexNormal);
+    vec3 fragTangent = normalize(normalMatrix*vertexTangent);
+    fragTangent = normalize(fragTangent - dot(fragTangent, fragNormal)*fragNormal);
+    vec3 fragBinormal = normalize(normalMatrix*vertexBinormal);
+    fragBinormal = cross(fragNormal, fragTangent);
+
+    TBN = transpose(mat3(fragTangent, fragBinormal, fragNormal));
+
+    // Calculate final vertex position
+    gl_Position = mvp * vec4(vertexPosition, 1.0);
+}