make typescript peer dependency optional

[nilzona]

This will eliminate warnings of missing peer dependencies when libraries like e.g. eslint-plugin-jest are used in a non typescript project.

 WARN  Issues with peer dependencies found
└─┬ eslint-plugin-jest 27.0.4
  └─┬ @typescript-eslint/utils 5.37.0
    └─┬ @typescript-eslint/typescript-estree 5.37.0
      └─┬ tsutils 3.21.0
        └── ✕ missing peer typescript@">=2.8.0 || >= 3.2.0-dev || >= 3.3.0-dev || >= 3.4.0-dev || >= 3.5.0-dev || >= 3.6.0-dev || >= 3.6.0-beta || >= 3.7.0-dev || >= 3.7.0-beta"
Peer dependencies that should be installed:
  typescript@>=2.8.0  

resolves #143