dev: use cssnano, postcss, postcss-cli and css-declaration-sorter packages for more control over minification

dev: exclude some files
dev: sort declarations alphabetically during minification

.gitignore

@@ -1,2 +1,9 @@
 /tmp.txt
 /commits.csv
+/node_modules
+/Theme/mod.css
+/Theme/ElegantFin-theme-nightly-min.css
+/Theme/assets/add-ons/custom-media-covers-nightly-min.css
+/Theme/assets/add-ons/media-bar-plugin-support-nightly-min.css
+/Theme/assets/add-ons/seamless-fork-compatibility-nightly.css
+/Theme/assets/add-ons/seamless-fork-compatibility-nightly-min.css

package.json

@@ -0,0 +1,18 @@
+{
+    "devDependencies": {
+        "css-declaration-sorter": "^7.4.0",
+        "cssnano": "^8.0.1",
+        "postcss": "^8.5.15",
+        "postcss-cli": "^11.0.1"
+    },
+    "scripts": {
+        "build:theme": "postcss ./Theme/ElegantFin-theme-nightly.css -o ./Theme/ElegantFin-jellyfin-theme-build-latest-minified.css",
+        "build:covers-addon": "postcss ./Theme/assets/add-ons/custom-media-covers-nightly.css -o ./Theme/assets/add-ons/custom-media-covers-latest-min.css",
+        "build:mediabar-addon": "postcss ./Theme/assets/add-ons/media-bar-plugin-support-nightly.css -o ./Theme/assets/add-ons/media-bar-plugin-support-latest-min.css",
+        "build:release": "npm run build:theme && npm run build:covers-addon && npm run build:mediabar-addon",
+        "watch:theme": "postcss ./Theme/ElegantFin-theme-nightly.css -o ./Theme/ElegantFin-theme-nightly-min.css --watch --verbose",
+        "watch:covers-addon": "postcss ./Theme/assets/add-ons/custom-media-covers-nightly.css -o ./Theme/assets/add-ons/custom-media-covers-nightly-min.css --watch --verbose",
+        "watch:mediabar-addon": "postcss ./Theme/assets/add-ons/media-bar-plugin-support-nightly.css -o ./Theme/assets/add-ons/media-bar-plugin-support-nightly-min.css --watch --verbose",
+        "watch:fixes-addon": "postcss ./Theme/assets/add-ons/seamless-fork-compatibility-nightly.css -o ./Theme/assets/add-ons/seamless-fork-compatibility-nightly-min.css --watch --verbose"
+    }
+}

postcss.config.js

@@ -0,0 +1,22 @@
+const cssDeclarationSorter = require('css-declaration-sorter');
+const cssnano = require('cssnano');
+
+module.exports = {
+	plugins: [
+		cssDeclarationSorter({
+			keepOverrides: true,
+			order: (a, b) => {
+				const aVar = a.startsWith('--');
+				const bVar = b.startsWith('--');
+
+				if (aVar && !bVar) return -1;
+				if (!aVar && bVar) return 1;
+
+				return a.localeCompare(b);
+			},
+		}),
+		cssnano({
+			preset: 'default',
+		}),
+	],
+};