Add ddev-selenium-standalone-chrome

These are the files installed by

ddev get ddev/ddev-selenium-standalone-chrome (deprecated)

or

ddev add-on get ddev/ddev-selenium-standalone-chrome

Closes #3493430

added 13 commits

• 6d48a033...890df552 - 12 commits from branch project:1.x
• 64e42b0a - Add ddev-selenium-standalone-chrome

Compare with previous version

merged