Test suite & CI

Hello @kevva, I just noticed that since Travis-CI is no longer working even for open source projects, maybe you should move to Github Actions.

However, I have installed the project locally, and the `npm run test` script fails.

⬇ XO suite output (click to expand)

```
> lpad-align@2.0.0 xo
> xo

index.js:1:1
✖ 1:1 Do not use "use strict" directive. unicorn/prefer-module
✖ 2:22 Do not use "require". unicorn/prefer-module
✖ 3:17 Do not use "require". unicorn/prefer-module
✖ 5:1 Do not use "module". unicorn/prefer-module
✖ 5:19 The variable str should be named string. A more descriptive name will do too. unicorn/prevent-abbreviations

cli.js:2:1
✖ 2:1 Do not use "use strict" directive. unicorn/prefer-module
✖ 3:18 Do not use "require". unicorn/prefer-module
✖ 4:14 Do not use "require". unicorn/prefer-module
✖ 5:19 Do not use "require". unicorn/prefer-module

9 errors
```

Ava suite output

```
> lpad-align@2.0.0 ava
> ava

× No tests found in test.js

─

Uncaught exception in test.js

/var/www/lpad-align/test.js:1
import test from 'ava';
^^^^^^

SyntaxError: Cannot use import statement outside a module

─

1 uncaught exception
```

Maybe it comes from the fact that the package is tested before being built, but there's no actual docs on how to build it.

Do you think it could be interesting to refresh or refactor the test suite somehow?

Start with the npm test script and the reported files index.js, cli.js, and test.js. Run npm run test to reproduce the XO and Ava failures, then inspect the existing Travis configuration and package scripts. Done means the test suite runs successfully and CI has a documented, working configuration, but the issue does not specify the intended migration scope.

Written by the indexing model from the issue text.