Add OpenTofu to community

[mediowen]

Reasons for making this change:

I'm a heavy user - basically just easier addition of OpenTofu-specific extensions, now that the project has extended that part of Terraform. Theoretically these could be added to Terraform.gitignore, but as the OpenTofu project progresses there may be more differences that aren't worth having both sides. Open to suggestion though.

Links to documentation supporting these rule changes:

• https://opentofu.org/docs/intro/whats-new/#override-files-for-opentofu-keeping-compatibility
• https://opentofu.org/docs/language/files/#file-extension
• https://opentofu.org/docs/language/files/override/

If this is a new template:

• Link to application or project’s homepage: https://opentofu.org/