Add padding-top value automatically if responsive medias have width and height attributes.

[oatw]

Why This Feature Should be Added to Luda

If a responsive media has width and height attribute, the padding-top value of its container should be calculated and set automatically to ensure the scale ratio.

How Should This Feature Work

1. Detect if a responsive media has width and height attribute.
2. Calculate padding-top value in percentage according to the width value and height value.
3. Set media wrapper padding-top value.

Additional context

Plan to release feature in version 0.3.3.