Adding "Add to calendar" links for multiple targets (Google, Outlook) to an email invitation

This is more work than one would guess. However, these were the first instructions that worked for me:

However, there must be a Chrome plugin to do all this? Or a java script? The instructions are using a combination of different online tools, which makes the process tedious...

If the instructions are correct, there is no way to add an event automatically to iCloud calendar short of importing an iCal file (which we do not want since it requires lots of manual clicking).