Added a Nix Flake and support for running from the Nix Store (#47)

* Added a Nix Flake and support for running from the Nix Store

* Removed variable imports since they're brough in at the top level.

* Removed redundan imports and remove unused files (moved to temp).

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Co-authored-by: Jas Singh <jaskiratpal.singh@outlook.com>

scss/style/osd/index.scss

@@ -1,6 +1,3 @@
-@import "../colors";
-@import '../../variables';
-
 .indicator {
   .osd-container {
     margin: $osd-margins;