update README - added plugin dev override

[abner-dou]

Description

Added block in README about how to override provider for dev plugin use

Link to any related issue(s):

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 Terraform 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

[leofigy]

LGTM

[abner-dou]

Hi @themantissa , I'm trying to add a mongo reviewer to this PR using apiX or @apiX but nothing appears :/
this may be a permissions issue?

[themantissa]

@abner-dou just tried and it's actually mongodb/apix try that and see if it works please.

[themantissa]

Thank you for adding this! LGTM

[threebee]

LGTM!