Add contributing guidelines

[adiati98]

Description

This PR adds contributing guidelines to the .github folder with details as follow:

• Using Mautic community handbook's contributing guidelines as a template, I addded important details to the guidelines specific to this repo:
  • Clone particular branch when working with a documentation version
  • How to work with each branch on GitHub Codespaces
• Added images
• Added a "Contributing" section to the README
• Removed the "Local development setup" and "Making a PR" section from the README as they've already explained in the contributing guidelines

Linked issue

Closes #441

Screenshots or screen recordings

[adiati98]

@RCheesley @favour-chibueze I have some questions and need confirmation:

1. I removed the Local development setup completely because we now have it in the contributing guidelines. I pointed contributors to the "Contributing" section on the README for complete contributing information.

   However, in the "Local development setup", we have "2. With Sphinx (Python application)" subsection about how to work directly with Sphinx.

   As we're encouraging folks to work with DDEV for convenience, do we want to remove or keep this section? FYI, I always have trouble setting up Python on my machine. So, if we'd like to keep this, I'll add it back as is.

2. We have the "Generating translations files" on the README. The instruction in this section is using sphinx-build -b gettext . docs_translations command. I tried this out, and I got prompted to install python3-sphinx. As I don't have Python installed on my machine, I need to install Python first. So, I can't test this out.

   Do we want to keep this section (and move it to the contributing guidelines) or remove it? FYI, we don't have any translation for this repo yet.

3. I have never worked with translation before. So, it'd be great if any of you could confirm that the "Translations" section in the User Documentation is still up to date.

TIA! ✨

[RCheesley]

1. However, in the "Local development setup", we have "2. With Sphinx (Python application)" subsection about how to work directly with Sphinx.
   As we're encouraging folks to work with DDEV for convenience, do we want to remove or keep this section? FYI, I always have trouble setting up Python on my machine. So, if we'd like to keep this, I'll add it back as is.

I'd recommend removing it.

2. We have the "Generating translations files" on the README. The instruction in this section is using sphinx-build -b gettext . docs_translations command. I tried this out, and I got prompted to install python3-sphinx. As I don't have Python installed on my machine, I need to install Python first. So, I can't test this out.
Do we want to keep this section (and move it to the contributing guidelines) or remove it? FYI, we don't have any translation for this repo yet.

Indeed, remove - we tried to set it up in the past but couldn't get it to work.

[adiati98]

Thanks for the response! I'll remove it once I'm back.

[adiati98]

@RCheesley I've removed the Sphinx and generating translation files sections.

[adiati98]

@all-contributors please add @adiati98 for docs

[allcontributors]

@adiati98

I've put up a pull request to add @adiati98! 🎉