Add reference file for font weight case

Modify 11 font weight cases and add 4 reference file.
Not sure if it is good/OK to use the same feature/property in reference file as that in test file.

As of this feature, most user agents support it, see https://test.csswg.org/harness/results/css-fonts-3_dev/grouped/section/3.2/

CC @rhauck