Deprecation Guide for Accessing named args via {{attrs}}

The {{attrs}} object was an alternative way to reference named arguments in templates that was introduced prior to named arguments syntax being finalized. References to properties on {{attrs}} can be converted directly to named argument syntax.

Before:

{{attrs.foo}}
{{this.attrs.foo.bar}}
{{deeply (nested attrs.foobar.baz)}}

After:

 {{@foo}}
 {{@foo.bar}}
 {{deeply (nested @foobar.baz)}}