Future dart-sass compat issue.

It looks like the future version of sass will not allow !global to declare a new variable.

DEPRECATION WARNING: As of Dart Sass 2.0.0, !global assignments won't be able to
declare new variables. Consider adding `$o-typography-font-scale: null` at the top level.

    ╷
219 │ ┌     $o-typography-font-scale: (
220 │ │        -2: (12, (12 * 1.2)),
221 │ │        -1: (14, (14 * 1.2)),
222 │ │         0: (16, (16 * 1.2)),
223 │ │         1: (18, (18 * 1.2)),
224 │ │         2: (20, (20 * 1.2)),
225 │ │         3: (24, (24 * 1.2)),
226 │ │         4: (28, (28 * 1.2)),
227 │ │         5: (32, (32 * 1.2)),
228 │ │         6: (40, (40 * 1.2)),
229 │ │         7: (48, (48 * 1.2)),
230 │ │         8: (56, (56 * 1.2)),
231 │ │         9: (72, (72 * 1.2)),
232 │ │        10: (84, (84 * 1.2)),
233 │ │     ) !default!global;
    │ └─────────────────────^
    ╵
    /var/folders/x0/9f0320m12jb3nmjcp8kdccw00000gr/T/4d58026c/bower_components/o-typography/src/scss/_brand.scss 219:5  @import
    /var/folders/x0/9f0320m12jb3nmjcp8kdccw00000gr/T/4d58026c/bower_components/o-typography/main.scss 6:9               @import
    /var/folders/x0/9f0320m12jb3nmjcp8kdccw00000gr/T/4d58026c/src/main.scss 1:62                                        root stylesheet

Financial-Times / o-typography

Future dart-sass compat issue. #193