Docs: improve optimize docs

Author: JPeer264

README.md

@@ -58,6 +58,7 @@ fs.writeFileSync('./dist/index.html', html);
 - [rcs.stats](docs/api/stats.md) (deprecated)
 - [rcs.replace](docs/api/replace.md)
 - [rcs.mapping](docs/api/mapping.md)
+- [rcs.optimize](docs/api/optimize.md)
 - [rcs.statistics](docs/api/statistics.md)
 - [rcs.baseLibrary](docs/api/baselibrary.md)
 - [rcs.fillLibraries](docs/api/filllibraries.md)

docs/api/optimize.md

@@ -0,0 +1,82 @@
+# rcs.optimize
+
+> Optimizes selectors based on the loaded statistics and given selectors
+
+> **Note:** Before this method takes effect you should either run [`rcs.fillLibraries`](./filllibraries.md) or load your mappings and statistics manually with [`rcs.mapping.load`](./mapping.md#load) and [`rcs.statistics.load`](./statistics.md#load)
+
+## Usage
+
+**rcs.optimize()**
+
+Example with `fillLibraries`:
+
+```js
+const rcs = require('rcs-core');
+
+rcs.fillLibraries(`
+  #my-id {
+    content: "";
+  }
+
+  .test-selector[class^="sel"] {
+    content: "";
+  }
+
+  .selector {
+    content: "";
+  }
+`)
+
+rcs.optimize();
+
+// now replace your selectors
+const css = rcs.replace.css(fs.readFileSync('./src/styles.css', 'utf8'));
+
+fs.writeFileSync('./dist/styles.css', css);
+```
+
+Example with `mapping.load` and `statistics.load`:
+
+```js
+// load mapping (could also come from a saved file)
+rcs.mapping.load({
+  selectors: {
+    '#test': 'a',
+    '.ca': 'a',
+    '.ba': 'b',
+    '.aa': 'c',
+  },
+});
+
+// load statistics (could also come from a saved file)
+rcs.statistics.load({
+  ids: {
+    unused: [],
+    usageCount: {
+      test: 2,
+    },
+  },
+  classes: {
+    unused: [],
+    usageCount: {
+      ca: 3,
+      ba: 10,
+    },
+  },
+  keyframes: {
+    unused: [],
+    usageCount: {},
+  },
+  cssVariables: {
+    unused: [],
+    usageCount: {},
+  },
+});
+
+rcs.optimize();
+
+// now replace your selectors
+const css = rcs.replace.css(fs.readFileSync('./src/styles.css', 'utf8'));
+
+fs.writeFileSync('./dist/styles.css', css);
+```