bump most of dependencies, update package.json

[Simek]

This PR introduces the following changes:

• bumps most of dependencies to the latest version (including minor release of Docusaurus V1)
  • Prettier was not updated because since 1.17.0+ Markdown tables format were changed to use the minimal required characters count instead of adjusting table to the content, AFAIK it's not configurable (@rachelnabors please let me know if it's a problem from your point of view, I can update Prettier in the separate PR)
• adds simple script (update-lock) to optimize the Yarn lockfile to the package.json
• adds homepage field to package.json
• replaces the license with the correct SPDX ID
• replaces repository field value in package.json with the shortcut
• removes main field from package.json (it's not required)
• switch CI Node image from 8 to LTS (12 currently)

There are also changes to the two Markdown files - it's the result of Prettier run on the current files.

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