feat: render per-vertex color triangle

- Add shader class for vertex/fragment program compilation
- Add vao class for vertex array object management
- Render RGB gradient triangle with interpolated vertex colors

cbt/opengl/vao.cpp

@@ -0,0 +1,47 @@
+#include "cbt/opengl/vao.hpp"
+
+namespace cbt::opengl {
+
+vao::vao() {
+    glGenVertexArrays(1, &m_id);
+}
+
+vao::~vao() {
+    if (m_id) {
+        glDeleteVertexArrays(1, &m_id);
+    }
+}
+
+vao::vao(vao&& other) noexcept
+    : m_id(other.m_id) {
+    other.m_id = 0;
+}
+
+vao& vao::operator=(vao&& other) noexcept {
+    if (this != &other) {
+        if (m_id) {
+            glDeleteVertexArrays(1, &m_id);
+        }
+        m_id = other.m_id;
+        other.m_id = 0;
+    }
+    return *this;
+}
+
+auto vao::bind() const -> void {
+    glBindVertexArray(m_id);
+}
+
+auto vao::unbind() const -> void {
+    glBindVertexArray(0);
+}
+
+auto vao::id() const -> GLuint {
+    return m_id;
+}
+
+auto vao::valid() const -> bool {
+    return m_id != 0;
+}
+
+}