Created raylib GLFW dependency (markdown)

raylib-GLFW-dependency.md

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+raylib uses [GLFW library](https://github.com/glfw/glfw) for several platforms Window/Input events management:
+
+  - `PLATFORM_DESKTOP` (Windows, Linux, macOS)
+  - `PLATFORM_WEB` (Html5) ([Emscripten JS implementation (limited)](https://github.com/emscripten-core/emscripten/blob/master/src/library_glfw.js))
+
+GLFW is used only on [core](https://github.com/raysan5/raylib/blob/master/src/core.c) module. 
+
+In case someone could be interested in replacing GLFW for a custom platform-specific implementation, here it is a list with the functions currently used (raylib 3.0):
+
+```c
+ // GLFW: Device init/close
+glfwInit();
+glfwInitHint(GLFW_COCOA_CHDIR_RESOURCES, GLFW_FALSE);
+glfwDefaultWindowHints();
+glfwWindowHint(GLFW_SCALE_TO_MONITOR, GLFW_TRUE);
+glfwCreateWindow(CORE.Window.display.width, CORE.Window.display.height, CORE.Window.title, glfwGetPrimaryMonitor(), NULL);
+glfwDestroyWindow(CORE.Window.handle);
+glfwWindowShouldClose(CORE.Window.handle);
+glfwSetWindowShouldClose(CORE.Window.handle, GLFW_TRUE);
+glfwMakeContextCurrent(CORE.Window.handle);
+glfwGetFramebufferSize(CORE.Window.handle, &fbWidth, &fbHeight);
+glfwWaitEvents();
+glfwPollEvents();
+glfwSwapInterval(1);
+glfwSwapBuffers(CORE.Window.handle);
+glfwTerminate();
+
+// GLFW: Window/Monitor management
+glfwGetWindowPos(CORE.Window.handle, &CORE.Window.position.x, &CORE.Window.position.y);
+glfwGetWindowAttrib(CORE.Window.handle, GLFW_VISIBLE) == GL_FALSE);
+glfwSetWindowTitle(CORE.Window.handle, title);
+glfwSetWindowPos(CORE.Window.handle, x, y);
+glfwGetPrimaryMonitor();
+glfwGetMonitors(&monitorCount);
+glfwGetMonitorName(monitors[monitor]));
+glfwGetMonitorPhysicalSize(monitors[monitor], &physicalWidth, NULL);
+glfwSetWindowMonitor(CORE.Window.handle, monitors[monitor], 0, 0, mode->width, mode->height, mode->refreshRate);
+glfwSetWindowSizeLimits(CORE.Window.handle, width, height, mode->width, mode->height);
+glfwSetWindowSize(CORE.Window.handle, width, height);
+glfwGetVideoMode(monitor);
+glfwShowWindow(CORE.Window.handle);
+glfwHideWindow(CORE.Window.handle);
+glfwGetWin32Window(CORE.Window.handle);
+glfwGetX11Window(window);
+glfwGetCocoaWindow(window);
+
+// GLFW: Misc functionality
+glfwGetProcAddress();
+glfwGetClipboardString(CORE.Window.handle);
+glfwSetClipboardString(CORE.Window.handle, text);
+glfwGetTime();
+
+// GLFW: Callbacks (Window/Input events)
+glfwSetErrorCallback(ErrorCallback);
+glfwSetWindowSizeCallback(CORE.Window.handle, WindowSizeCallback);
+glfwSetWindowIconifyCallback(CORE.Window.handle, WindowIconifyCallback);
+glfwSetWindowFocusCallback(CORE.Window.handle, WindowFocusCallback);
+glfwSetCursorEnterCallback(CORE.Window.handle, CursorEnterCallback);
+glfwSetCursorPosCallback(CORE.Window.handle, MouseCursorPosCallback);
+glfwSetMouseButtonCallback(CORE.Window.handle, MouseButtonCallback);
+glfwSetScrollCallback(CORE.Window.handle, ScrollCallback);
+glfwSetKeyCallback(CORE.Window.handle, KeyCallback);
+glfwSetCharCallback(CORE.Window.handle, CharCallback);
+glfwSetDropCallback(CORE.Window.handle, WindowDropCallback);
+
+// GLFW: Input management
+// NOTE: Most inputs (keyboard/mouse) are managed through callbacks
+glfwJoystickPresent(i);
+glfwGetJoystickName(gamepad);
+glfwGetGamepadState(i, &state);
+glfwSetInputMode(CORE.Window.handle, GLFW_CURSOR, GLFW_CURSOR_NORMAL);
+glfwSetCursorPos(CORE.Window.handle, CORE.Input.Mouse.position.x, CORE.Input.Mouse.position.y);
+```
+
+GLFW is NOT used on the following platforms, where custom implementations are used to manage Window/Inputs:
+
+  - `PLATFORM_ANDROID`-> Uses `native_app_glue` Android NDK module
+  - `PLATFORM_RPI`(native, no desktop) -> Uses `EGL`, `evdev` and standard system libraries directly
+  - `PLATFORM_UWP`-> Uses UWP provided libraries