Configuration should be versioned

[bendrucker]

The configuration here is implicitly associated with the version of TFLint that runs it. In the future, new versions of TFLint could make breaking changes, such as removing top level configuration, rules, etc. When we update this config to match, that will also be a breaking change. It is unsafe for other repos to refer to the default branch in this repo.

Configuration should be versioned with semver major/minor/full tags so that consumers can initially refer to v1 and receive only non-breaking updates.

In the future we might look at specifying the TFLint version in this config:

terraform-linters/tflint#1217

The required_version (or similar) could be parsed out of the config and used to download the latest matching TFLint version. This seems like yet another use case for an action that can do semver constraint resolution on a list of GitHub releases.