feat: styled API; monorepo grooming

[tassoevan]

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• Lint and unit tests pass locally with my changes
• I have labeled the PR correctly with the related package
• I have run Loki's visual regression tests (if applicable)
• I have added tests that prove my fix is effective or that my feature works (if applicable)
• I have added necessary documentation (if applicable)
• Any dependent changes have been merged and published in downstream modules

Proposed changes (including videos or screenshots)

This PR:

• adds an hygen template for creating new library packages (accessible via yarn create-package library);
• adds the @rocket.chat/styled package as a PoC;
• upgrades all dependencies.

Issue(s)

Further comments

[lgtm-com]

This pull request introduces 1 alert when merging 8a45932 into b028da8 - view on LGTM.com

new alerts:

• 1 for Syntax error