Cleanup repository

[JoviDeCroock]

• remove bors.toml unused
• remove appveyor.yml unused
• replace travis-size-report with our own compressed-size-action
• introduce npm deps caching on the github-actions

[changeset-bot]

⚠️ No Changeset found

Latest commit: e17611c

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[rschristian]

Sorry, went to bed after hitting approve this morning