CSS variables not being evaluated/highlighting

I use Pigments in SVG files, and while the colors are highlighted in CSS variable declarations, they are _not_ highlighted when the variable is used:

I checked to see if it was just a problem with inline properties, or just SVG, but it also occurs in HTML:

When I run `Pigments: Reload` on an open project I get the following:
```
Found:

90 path(s)
0 variables(s) including 0 color(s)
```
(there are a whole lot of color variables in this project)

From having a look through the issues, it seems that this is working for most other people - is there a setting that I should check on? I think I still have mostly the defaults though.

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Pigments version: **0.40.6**
Atom version: **1.53.0**
OS: **elementary OS 5.17** (Built on Ubuntu 18.04.4 LTS)