Add Ansible Community Forum to "Get Involved" section of README

[kurokobo]

Please confirm the following

• I agree to follow this project's code of conduct.
• I have checked the current issues for duplicates.
• I understand that AWX is open source software provided for free and that I might not receive a timely response.

Feature type

New Feature

Feature Summary

If users want to ask something, the newly opened Ansible Community Forum is the good place to do so.

Currently in this repository, if a usage question comes in that is not a bug report or RFE, the "Get Involved" section of the README is provided as the place to reffer, but it would be nice to have a mention of the Ansible Community Forum there.

Select the relevant components

• UI
• API
• Docs
• Collection
• CLI
• Other

Steps to reproduce

See "Get Involved" section of README: https://github.com/ansible/awx#get-involved

Current results

No information about Ansible Community Forum is provided

Sugested feature result

Users can refer to the Ansible Community Forum to ask questions.

Additional information

N/A

[kurokobo]

Closed via #14472

@TheRealHaoLiu
Thanks for updating the docs!