INTMDB-720: [Terraform] Investigate ChangeLog Generator

[andreaangiolillo]

Description

As part of INTMDB-720, we discovered how we can automatically generate CHANGELOG.md with the format that we want. This requires us to add labels to the PR that we want to show in specific sections of the changelog.

Proposed Changes:
This PR updates the PR template to explain when we should add the label and which label to use depending on the PR change and create a RELEASING.md file to include the correct command to generate the CHANGELOG.md.

Type of change:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Documentation fix/enhancement

Required Checklist:

• I have signed the MongoDB CLA
• I have read the contribution guidelines
• I have added tests that prove my fix is effective or that my feature works per HashiCorp requirements
• I have added any necessary documentation (if appropriate)
• I have run make fmt and formatted my code

Further comments

[Zuhairahmed]

LGTM! @martinstibbe @maastha @evertsd can you make sure to add these labels to your future PRs as well ChangeLog Generator can pick up for us. Thank you!