Adapt to syntax theme

[hironytic]

With this patch,

becomes

("Base16 Tomorrow Dark" theme is selected in this screenshot.)

[miketheman]

This looks correct - however I was looking for some docs on the distinction between syntax-variables and ui-variables - do you know where I can find them?

[hironytic]

I don't know much. 😔
In fact, I searched over docs before PR but I couldn't find it.

This document mentions UI theme and syntax theme. But I'm not sure ui-variables and syntax-variables are them.

[hironytic]

It turns out that syntax-variables should be imported.

Importing ui-variables works if UI theme is 'One Dark', but it doesn't if UI theme is 'Atom Dark'. Because

• One Dark imports syntax-variables in its ui-variables.less
• Atom Dark doesn't import syntax-variables.

I also found in Atom Template Syntax Theme,

• Define proper colors in your syntax-variables.less file. Other packages
  can use these variables. All the variables defined in this package's
  syntax-variables.less file must be defined — you cannot pick and choose.

and @syntax-color-(added|modified|removed) was defined in syntax-variables.less.

[miketheman]

Thanks for looking into the details. Merging and releasing now.