.pre-commit-config.yaml

* Exclude sigv4 test suite from pre-commit file endings hook
* Upgrade Ktlint
* Make Gradle ktlint target consistent with pre-commit

They were previously running two separate rulesets since pre-commit
pulls in the standard ruleset, and that wasn't pulled into the Gradle
dependencies.

* Fix Gradle Ktlint paths
* Establish editorconfig for Ktlint
* Fix Ktlint lints
* Enable `trailing-commas` rule
* Fix block quote indentation