…erv#406)

* Update 28_model_loading.cpp

Removed "warn" argument passed to tinyobj::LoadObj(...).

* Update 29_mipmapping.cpp

Removed "warn" argument passed to tinyobj::LoadObj(...).

* Update 30_multisampling.cpp

Removed "warn" argument passed to tinyobj::LoadObj(...).

* Update 08_Loading_models.md

Removed "warn" argument passed to tinyobj::LoadObj(...) from e-book.

* Update 08_Charger_des_modèles.md

Removed "warn" argument passed to tinyobj::LoadObj(...).

Whoever wants to shrink the margins, they can now do so via the new
optional command line arguments

--geometry:left
--geometry:right
--geometry:top
--geometry:bottom

which are default options in pandoc (see pandoc's documentation
[here](https://pandoc.org/demo/example33/6.2-variables.html)).

Their default value is ''. These options are not passed to pandoc when
their value is ''.

The argument parser added can be extended easily with other pandoc's
argument options. If the new options' default value is '' then they will
not be passed to pandoc.

Almost all of the code listed in this chapter uses a c++ code block. The
block for the 'GLFWWindow* window' was missing.

* Fix typo in the html generation instructions.

* Add a code block for the GLFW window pointer.

Almost all of the code listed in this chapter uses a c++ code block. The
block for the 'GLFWWindow* window' was missing.