Add DEVELOPMENT.md

[jamesponddotco]

What does this PR do?

Add a DEVELOPMENT.md file with guidelines and instructions on how to develop pkgdex. Closes #1.

Review checklist

Before submitting your PR, please review the following:

• I have read the CONTRIBUTING.md file.
• My changes are focused and address a single concern.
• I have added/updated tests that prove my fix is effective or that
  my feature works.
• New and existing tests pass locally with my changes.
• I have added necessary documentation or made changes to
  documentation (if appropriate).
• My changes generate no new warnings or errors.
• My code follows the code style of this project.

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• The contribution is my own original work.
• I have the right to submit it under the project's license.
• I understand and agree to the project's contributing guidelines.

[Rayuaz]

There are some problems with the make file, but that's not directly related to the changes in this PR. I'll create a new PR to fix those issues.

[jamesponddotco]

@Rayuaz Sorry for the delay, I can only work on this at night, but I have driving classes at night now, since I'm trying to get my license. I'll work on the issues you raised this weekend. Thanks for the review!

[jamesponddotco]

@Rayuaz When you have a second, can you review again, please?