feat(animation): add motion tokens

[srambach]

Fixes #52

@mcoker @lboehling @kaylachumley Do you think the base tokens (like --pf-t--global--delay--400) should have "motion" in them?

@mcoker Is it ok to include these in the -default scss file?

[mcoker]

@mcoker @lboehling @kaylachumley Do you think the base tokens (like --pf-t--global--delay--400) should have "motion" in them?

@srambach I'm curious if others have an opinion. A little bit on what I'm thinking is...

Pros to not including --motion:

• Vars are shorter, which isn't terribly important but it's more than zero importance!
• Naming is more flexible so they could be used with other non-motion semantic tokens without the naming being potentially confusing. This implies they may be used for things other than --motion tokens

Pros to including --motion:

• being more clear as to what these apply to. Everything is under --pf-t--global--motion. Implies these base tokens will probably only apply to --pf-t--global--motion semantic vars
• avoiding namespace conflicts if we introduced different base delays/durations for some other non-motion tokens

@mcoker Is it ok to include these in the -default scss file?

I don't see why not. Is there a potential issue you can think of? Is it a question of whether we need an additional token file (like -motion or something)?

[mcoker]

lgtm! just one comment about an update to build.js

[mcoker]

Just wanted to make sure this change was intentional 👍

[srambach]

Closing in favor of #56, which brings in the relevant tokens.
As to naming... let's go with this for the moment.
And motion tokens are included in the default scss token file.