Bump all dependencies to latest

[aduth]

Why:

• Reduce number of npm audit issues
• Minimize future maintenance burden caused by larger version drift
• Prepare for 6.0.0 release

Major version updates:

cssnano 4.1.10 to 5.0.4

• Changelog: https://github.com/cssnano/cssnano/releases/tag/cssnano%405.0.0
  • No relevant changes needed

gulp-notify 3.2.0 to 4.0.0

• Changelog: https://github.com/mikaelbr/gulp-notify/blob/master/CHANGELOG.md#v400
  • No relevant changes needed

gulp-sourcemaps 2.6.5 to 3.0.0

• Changelog: https://github.com/gulp-sourcemaps/gulp-sourcemaps/releases/tag/v3.0.0
  • No relevant changes needed

jest 26.6.0 to 27.0.1

• Changelog: https://jestjs.io/blog/2021/05/25/jest-27#miscellaneous-breaking-changes
  • No relevant changes needed

jest-puppeteer 4.4.0 to 5.0.4

• Changelog: https://github.com/smooth-code/jest-puppeteer/releases/tag/v5.0.0
  • No relevant changes needed

puppeteer 5.3.1 to 9.1.1

• Changelog:
  • https://github.com/puppeteer/puppeteer/blob/main/CHANGELOG.md#900-2021-04-21
    • No relevant changes needed
  • https://github.com/puppeteer/puppeteer/blob/main/CHANGELOG.md#800-2021-02-26
    • No relevant changes needed
  • https://github.com/puppeteer/puppeteer/blob/main/CHANGELOG.md#700-2021-02-03
    • No relevant changes needed
  • https://github.com/puppeteer/puppeteer/blob/main/CHANGELOG.md#600-2021-02-02
    • No relevant changes needed

[zachmargolis]

LGTM

[aduth]

There were a few updates released over the weekend.

 cssnano                ^5.0.4  →   ^5.0.5     
 eslint-plugin-import  ^2.23.3  →  ^2.23.4     
 jest                  ^27.0.1  →  ^27.0.3     
 puppeteer              ^9.1.1  →  ^10.0.0 

I'll plan to incorporate the bug-fix releases. It appears Puppeteer@10 isn't (yet) compatible with jest-puppeteer:

npm WARN [email protected] requires a peer of puppeteer@>= 1.5.0 < 10 but none is installed. You must install peer dependencies yourself.

I don't see anything as especially pressing from the release notes, so I think we can deal with that upgrade later, once jest-puppeteer has a chance to catch up.