Converting a nim string to a ptr GlChar

[def_pri_pub]

Right now I'm trying to get a simple OpenGL ES example working with Nimious' GL 
ES bindings. I'm hitting a bit of a wall when trying to get the proc 
glShaderSource() to accept my shader's source code (which is gotten through the 
readFile() proc, which outputs a nim string). Here is a link to that proc: 
[https://github.com/nimious/gles/blob/master/src/gles2/gl2.nim#L1545](https://github.com/nimious/gles/blob/master/src/gles2/gl2.nim#L1545)

In C, this usually is the way someone loads a shader source: 
    
    
    const char* vertexShaderSrc =
    "#version 400"
    ""
    "in vec3 pos;"
    ""
    "void main() {"
    "  gl_Position = vec4(pos, 1.0);"
    "}";
    
    // ...
    
    GLuint vertShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertShader, 1, &vertexShaderSrc, NULL)
    
    

I'm fine up until that 3rd parameter to something that GLES' glShaderSource() 
proc will accept? It needs a ptr ptr GlChar. [GlChar is defined 
here](https://github.com/nimious/gles/blob/master/src/gles2/gl2.nim#L22)