Add the .gitattributes in order to hide some folders/files from linguist

[erikyo]

What problem does this address?

Currently are counted by linguist files that are not really part of this repo, for example the storybook assets folder which uses all the WordPress backend styles or package.json which is a generated file

What is your proposed solution?

add a .gitattributes with an exclusion like the following:

# remove generated / documentation 
package.json linguist-generated=true
/src/stories/** linguist-vendored=true