Acronyms incorrectly detected as upper-case

## Faulty Behavior

```
fix: JTD types -> JSON schema types
```

```
✖ subject must not be sentence-case, start-case, pascal-case, upper-case [subject-case]
```

The above fails as the linter detects the subject as being upper-case, even though it's just an acronym.

## Affected packages

- [ ] cli
- [x] core
- [ ] prompt
- [ ] config-angular

## Possible Solution

Check that _all_ letters in the word are uppercase and assume it's an acronym, ignoring any title-case lints. Skip for 1 letter words.

## Steps to Reproduce (for bugs)

Lint the above commit message with `@commitlint/config-conventional`.

## Your Environment

| Executable | Version |
| ---------------------: | :------ |
| `commitlint --version` | 17.0.3 |
| `git --version` | 2.34.1|
| `node --version` | 16.15.1 |
| `@commitlint/config-conventional` | 17.0.3 |