[doc] update developer quickstart guide

- Add yourself to the :origin:`AUTHORS.rst` file.

- Choose meaning full commit messages, read `Conventional Commits`_

- Choose meaningful commit messages, read `Conventional Commits`_

  .. code::

Development Quickstart

======================

.. sidebar:: :ref:`makefile`

.. _npm: https://www.npmjs.com/

   For additional developer purpose there are :ref:`makefile`.

This quickstart guide gets your environment set up with searx.  Furthermore, it

gives a short introduction to the ``manage.sh`` script.

How to setup your development environment

=========================================

.. sidebar:: :ref:`make pyenv <make pyenv>`

   Alternatively use the :ref:`make pyenv`.

First, clone the source code of searx to the desired folder.  In this case the

source is cloned to ``~/myprojects/searx``.  Then create and activate the

searx-ve virtualenv and install the required packages using ``manage.sh``.

Searx loves developers, just clone and start hacking.  All the rest is done for

you simply by using :ref:`make <makefile>`.

.. code:: sh

    cd ~/myprojects

    git clone https://github.com/searx/searx.git

    cd searx

    python3 -m venv searx-ve

    . ./searx-ve/bin/activate

    ./manage.sh update_dev_packages

How to run tests

================

.. sidebar:: :ref:`make test.unit <make test>`

   Alternatively use the ``test.pep8``, ``test.unit``, ``test.robot`` targets.

Tests can be run using the ``manage.sh`` script.  Following tests and checks are

available:

- Unit tests

- Selenium tests

- PEP8 validation

- Unit test coverage check

For example unit tests are run with the command below:

.. code:: sh

   ./manage.sh unit_tests

For further test options, please consult the help of the ``manage.sh`` script or

read :ref:`make test`.

How to compile styles and javascript

====================================

Here is how a minimal workflow looks like:

.. _less: https://lesscss.org/

.. _NodeJS: https://nodejs.org

1. *start* hacking

2. *run* your code: :ref:`make run`

3. *test* your code: :ref:`make test`

How to build styles

-------------------

If you think at some point something fails, go back to *start*.  Otherwise,

choose a meaningful commit message and we are happy to receive your pull

request. To not end in *wild west* we have some directives, please pay attention

to our ":ref:`how to contribute`" guideline.

Less_ is required to build the styles of searx.  Less_ can be installed using

either NodeJS_ or Apt.

If you implement themes, you will need to compile styles and JavaScript before

*run*.

.. code:: sh

   sudo -H apt-get install nodejs

   sudo -H npm install -g less

OR

.. code:: sh

   sudo -H apt-get install node-less

After satisfying the requirements styles can be build using ``manage.sh``

.. code:: sh

   ./manage.sh styles

How to build the source of the themes

=====================================

.. _grunt: https://gruntjs.com/

Grunt_ must be installed in order to build the javascript sources. It depends on

NodeJS, so first Node has to be installed.

   make themes

.. code:: sh

Don't forget to install npm_ first.

   sudo -H apt-get install nodejs

   make node.env

.. tabs::

After installing grunt, the files can be built using the following command:

   .. group-tab:: Ubuntu / debian

      .. code:: sh

   make themes

         sudo -H apt-get install npm

Tips for debugging/development

==============================

   .. group-tab:: Arch Linux

.. sidebar:: :ref:`make run`

      .. code-block:: sh

   Makefile target ``run`` already enables debug option for your developer

   session / see :ref:`make run`.

         sudo -H pacman -S npm

Turn on debug logging

  Whether you are working on a new engine or trying to eliminate a bug, it is

  always a good idea to turn on debug logging.  When debug logging is enabled a

  stack trace appears, instead of the cryptic ``Internal Server Error``

  message. It can be turned on by setting ``debug: False`` to ``debug: True`` in

  :origin:`settings.yml <searx/settings.yml>`.

   .. group-tab::  Fedora / RHEL

.. sidebar:: :ref:`make test`

      .. code-block:: sh

   Alternatively use the :ref:`make test` targets.

	 sudo -H dnf install npm

Run ``./manage.sh tests`` before creating a PR.

  Failing build on Travis is common because of PEP8 checks.  So a new commit

  must be created containing these format fixes.  This phase can be skipped if

  ``./manage.sh tests`` is run locally before creating a PR.