Clarify licensing info

[petekubiak]

Changes:

• Added license statement to README
• Added license field to Cargo.toml

Fixes #30.

[github-actions]

✅MegaLinter analysis: Success

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
✅ ACTION	actionlint	3		0	0	0.02s
✅ JSON	jsonlint	3		0	0	0.11s
✅ JSON	prettier	3	0	0	0	0.32s
✅ MARKDOWN	markdownlint	6	0	0	0	0.45s
✅ MARKDOWN	markdown-table-formatter	6	0	0	0	0.18s
✅ RUST	clippy	yes		no	no	52.68s
✅ YAML	prettier	5	0	0	0	0.37s
✅ YAML	yamllint	5		0	0	0.3s

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Your project could benefit from a custom flavor, which would allow you to run only the linters you need, and thus improve runtime performances. (Skip this info by defining FLAVOR_SUGGESTIONS: false)

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• Command: npx mega-linter-runner@9.2.0 --custom-flavor-setup --custom-flavor-linters ACTION_ACTIONLINT,JSON_JSONLINT,JSON_PRETTIER,MARKDOWN_MARKDOWNLINT,MARKDOWN_MARKDOWN_TABLE_FORMATTER,RUST_CLIPPY,YAML_PRETTIER,YAML_YAMLLINT

[github-actions]

MegaLinter has automatically applied linters fixes on this PR.
Please review the changes and merge if they are correct.
PR: #33