Updated External dependencies (markdown)

External-dependencies.md

@@ -19,6 +19,18 @@ Library | Used Version | raylib module | Notes
 [pthread Win32](https://www.sourceware.org/pthreads-win32/) | 2.9.1 | [physac](https://github.com/raysan5/raylib/blob/develop/src/physac.h) | POSIX style threads on Windows
 [lua](https://www.lua.org/about.html) | 5.3.3 | [rlua](https://github.com/raysan5/raylib/blob/develop/src/rlua.h) | raylib lua binding
 
+Note that raylib support multiple platforms and, consequently, not all library dependencies from above are the same for all the platforms. As commented, some of the above libraries included in raylib are single-file header-only libraries (`stb_image`, `stb_image_write`, `stb_image_resize`, `stb_vorbis`, `jar_mod`, `jar_xm`, `glad`), those libraries only depend on the C standard library for the target platform (libc, bionic) and are compiled together with raylib, no need for additional library linkage. But some other libraries are required with external linkage. Here it is a detailed list:
+
+PLATFORM | external dependencies | Notes
+--- | :---: | ---
+DESKTOP:Windows | `GLFW3`, `OpenGL`, `OpenAL` | Note that GLFW3 also requires linkage with `libgdi32`
+DESKTOP:Linux | `GLFW3`, `OpenGL`, `OpenAL` | Note that Linux also requires linkage with `libm`(math), `pthreads`(POSIX threads), `dl`(dynamic loading). Note that GLFW3 also requires linkage with `XWindows` specific libs: `X11`, `Xrandr`, `Xinerama`, `Xi`, `Xxf86vm` and `Xcursor`
+DESKTOP:OSX | `GLFW3`, `OpenGL`, `OpenAL` | Note that GLFW3 also requires linkage with `Cocoa` framework
+Android | `EGL`, `OpenGLES2.0`, `OpenAL` | Note that code must be compiled using `Android NDK` libraries, `android_native_app_glue` module is included in raylib shared library compilation and `OpenAL` android implementation also requires linkage against `OpenSLES` audio library.
+Raspberry Pi | `EGL`, `OpenGLES2.0`, `OpenAL`, `bcm_host` | Note that the only external libraries required (aside of the default ones that come with the system) is `OpenAL`, graphics run in native mode (no `XWindows` required) and inputs are read also natively (no `XWindows` input events)
+HTML5 (Web) | `GLFW3`, `WebGL`, `OpenAL` | Note that code must be compiled using `emscripten SDK`, all required libraries are included in the package, actually it uses javascript versions of `GLFW3` (incomplete implementation) and `OpenAL` (features limited).
+
+One of the raylib goals is to keep external dependencies to minimum and so I keep working to reduce this list as much as possible.