Allow assign directive to chain directly off of the tagname interpolation

[electrovir]

Allow this:

<${MyElement.assign({
    inputs: 'blah'
})}><${MyElement}>

instead of this:

<${MyElement}
    ${assign({
        inputs: 'blah'
    })}
><${MyElement}>

[electrovir]

possible way to do this:

1. add assign method to DelcarativeElementDefinition which returns itself
2. when assign is called on DelcarativeElementDefinition, it assigns the input values to a new "assigned input" property on the created DelcarativeElementDefinition
3. assign will have to return a new instance of the DelcarativeElementDefinition so as to not modify the original instance.
4. The HTML template mapper will then check to see if this "assigned input" property is set, and if it is, it will extract it and modify the mapped template to include a value in the template that is a call to the assign directive..

[electrovir]

released in v14.1.0