Upgrade dependent packages to the latest version

[yhatt]

This PR will upgrade development dependent packages to the latest version via yarn upgrade --latest.

Notable changes

• We have bumped Marp Core v1.3.0 and Marp CLI v0.21.1.
  • Included an improved polyfill for Safari and much better slide controling via content-visibility in the outputted HTML.
  • A regression when exporting PDF, PPTX, and images with Snap Chromium in Linux was fixed. Fix CLIError when exporting to PDF: dir option must be relative to "/tmp" #166.
    • NOTE: If both of VS Code and Chromium have installed by snap, the export command may fail due to AppArmor (Failed converting Markdown when running inside VSCode (snap) terminal marp-cli#287). As a workaround, try to set chrome path in the extension setting: /snap/chromium/current/usr/lib/chromium-browser/chrome (Failed converting Markdown when running inside VSCode (snap) terminal marp-cli#287 (comment)).
• Added test environment against Node for Electron 9: Node 12.14.1.
• There are a lot of updates for development environment: TypeScript v4, rollup plugins, and ESLint plugins.