chore: update plugin

[Tony133]

Proposals:

• Added neostandard dependency, so that it is aligned with all other Fastify plugins
• Removed .prettierrc.json
• Removed eslint-config-prettierand eslint-plugin-prettier dependencies
• Removed .taprc file, because the tests have all been converted with node:test
• Group all tests inside the test folder
• Indentation update with eslint and neostandard
• Update eslint.config.js file
• Minor improvements in the README.md
• Update tsconfig.json
• Minor improvements in the files index.d.ts and index.test-d.ts

Notes for future updates:

• Verify that there are no duplicate test cases ( It seems that the two e2e tests are very similar ) perhaps in a separate PR.