feat(server): add the possibility to attach an api key

[mdevolde]

feat(server): add the possibility to attach an api key

Why the pull request was made

To permit to users who have premium tokens to use the library with them.

Summary of changes

• Add a premium_key attribute in LanguageTool class.
• Use this attribute in LanguageTool._create_params
• Edit documentation to mention it.

Screenshots (if appropriate):

Not applicable.

How has this been tested?

With local tests. Miss an API key to test the feature.

Resources

Not applicable.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update (changes to documentation only)
• Refactor / code style update (non-breaking change that improves code structure or readability)
• Tests / CI improvement (adding or updating tests or CI configuration only)
• Other (please describe):

Checklist

• Followed the project's contributing guidelines.
• Updated any relevant tests.
• Updated any relevant documentation.
• Added comments to your code where necessary.
• Formatted your code, run the linters, checked types and tests.