Fix sw scope for non wp-content Wordpress setups

[jkasten2]

Description

One Line summary

Fix ServiceWorker scope path for Wordpress setups that do not use "wp-content" as part of their app. Example such as Bedrock.

Details

• Some Wordpress setups (such as roots/bedrock) use "app" instead of "wp-content" as URL path.
• Instead of assuming "wp-content" is present we always use the full path URL.
  • Created a getOneSignalPluginPath function to generate the path without the domain to provide this.

Tested

• Standard Wordpress 5.7
• presslabs/wordpress-runtime:bedrock docker image w/ Wordpress 5.7 to ensure it works end-to-end.

Related

• PR - Move off SW root scope for new installs #268
• Issue - Installing service worker failed (non wp-content directory structure) #273

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