feat: theme files are now loaded & applied on startup

src/themes/Blood.scss

@@ -0,0 +1,10 @@
+$foreground: red;
+$background: black;
+
+span {
+  color: $foreground;
+}
+
+.sidebar--WvRg_ {
+  background-color: $background;
+}

src/themes/csstest.css

@@ -1,3 +0,0 @@
-h2 {
-  color: black;
-}

src/themes/test.scss

@@ -1,7 +0,0 @@
-h1 {
-  color: black;
-
-  .title {
-    color: blue;
-  }
-}