Add some info about Gunicorn

[Raruto]

As per v3.4, this is what is currently reported in the /scripts/docker-entrypoint.sh file::

g3w-suite-docker/scripts/docker-entrypoint.sh

Lines 37 to 44 in e435dcc

	gunicorn base.wsgi:application \
	--limit-request-fields 0 \
	--error-logfile - \
	--log-level=debug \
	--timeout ${G3WSUITE_GUNICORN_TIMEOUT:-120} \
	--workers=${G3WSUITE_GUNICORN_NUM_WORKERS:-8} \
	--max-requests=${G3WSUITE_GUNICORN_MAX_REQUESTS:-200} \
	-b 0.0.0.0:8000

But currently the README.md file reports this stack without any other mention of gunicorn:

This is what we can currently find in the documentation:

• https://g3w-suite.readthedocs.io/en/latest/install.html?highlight=gunicorn#deploy-g3w-suite
• https://g3w-suite.readthedocs.io/en/latest/docker_env.html?highlight=gunicorn#gunicorn-settings

[Raruto]

For example, the following might be a useful local development tip (in order to speed up container startup times):

G3WSUITE_GUNICORN_NUM_WORKERS=1

[Raruto]

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Source: https://docs.gunicorn.org/en/stable/configure.html

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Gunicorn reads configuration information from five places (in order of least to most authoritative:):

1. Environment Variables
2. Framework Settings (see also: Django integration)
3. Configuration File (eg. gunicorn.conf.py) related to: #79
4. GUNICORN_CMD_ARGS
5. Command Line

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Source: https://docs.gunicorn.org/en/stable/index.html

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Gunicorn (‘Green Unicorn’) is a Python WSGI HTTP Server for UNIX broadly compatible with various web frameworks, simply implemented, light on server resources, and fairly speedy.

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Source: https://docs.gunicorn.org/en/stable/deploy.html

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It's strongly recommend using Gunicorn behind a proxy server. although there are many HTTP proxies available, we strongly advise that you use Nginx. If you choose another proxy server you need to make sure that it buffers slow clients when you use default Gunicorn workers. Without this buffering Gunicorn will be easily susceptible to denial-of-service attacks. You can use Hey to check if your proxy is behaving properly.

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