feat: Added config.yml file for welcome bot

[m-code12]

Issue that this pull request solves

Closes: #57

What is the change?

Created config.yml file for the welcome bot to help first-time contributors. To activate the app you need to go to https://github.com/apps/welcome and click on install and give the app the required permissions (Pull requests: Read & Write Issues: Read & Write).

How was it tested?

I have tested the welcome bot with the config.yml file in my personal repository. Here is a link to the repo: https://github.com/m-code12/WelcomeBot

Submissions guide:

• [ ] Have you made corresponding changes to the documentation?
• [x] Your submission doesn't break any existing feature.
• [ ] Have you lint your code locally prior to submission?

[welcome[bot]]

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