Clarify "missing web assets directory" error message

[dotNetkow]

Update the error message displayed when a user tries to add a native platform to their project, before having built their web code.

Changes:

• Fix the More Info link to point to the correct page (/basics/building-your-app instead of /basics/configuring-your-app).
• Help the user by telling them which property to change in capacitor config (webDir).
• Added build details for both Ionic apps and non-Ionic apps.

Wasn't sure how to format correctly for newlines - this function doesn't use log("") like the others.

[imhoffd]

It's using template literals. Newlines are printed as-in onto the screen. It actually preserves your spaces too so it prints kinda weird, like this:

Capacitor could not find the web assets directory "./www".
    Please create it and make sure it has an index.html file. You can change
    the path of this directory in capacitor.config.json (webDir option). You may need ...