Changes to quick-start guide

[sidd3888]

Made substantial changes to the structure of the quick start guide.

• Emphasised installation using pip whether using an Anaconda or Miniconda distribution or the standard PyPI install
• Shortened the guide to remove unnecessary elements for a beginner, including the section on testing out HARK using Spyder
• Removed redundancies such as repeated instructions on creating virtual environments
• Streamlined most of the content to make it more beginner friendly

I have removed the part on installing HARK using conda-forge, as I think it can be relegated to the installation guide alone. The quick start should serve its primary purpose by providing a single best way to get started.

[AA-Turner]

A few suggestions aimed at simplifying the quick-start guide.

A

[AA-Turner]

I think we ought recommend conda, perhaps replace the rest of this sub-section with the following?

To create a new environment, follow the steps below in your command line:

1. We first set up a Conda 'environment' for HARK.
   This is a way of isolating the installation of HARK so that it does not interfere
   with any other Python scripts or modules on your computer.
   To do so, at a command line type:

   ```console
   $ conda create -n econ-ark "python=3.10"
   ```

2. Activate the environment:

   ```console
   $ conda activate econ-ark
   ```

3. Install HARK into the environment:

   ```console
   (econ-ark) $ conda install econ-ark
   ```

I'd also consider remove the line about installing a non-default release, I'm unsure if it fits in the quick-start guide.

[AA-Turner]

Arguably this doesn't belong in the quick-start guide -- perhaps just redirect to the contributing guide?

[AA-Turner]

This sub-section should go within "Learning HARK" below

[alanlujan91]

@sidd3888 can you look at @AA-Turner's comments and make appropriate changes so we can merge this PR?

[sidd3888]

Have made changes according to @AA-Turner's suggestions. The only thing in which I differ was recommending the installation using conda-forge, as it seemed to be more prone to conflicts than the pip version, particularly because it installs older versions of everything else. That said, I have decluttered all other parts of the guide. If this sounds good, then lets go ahead with it. If we must insist on conda-forge, then I can make that change too.