📝 Polish onboarding and add feature examples

examples/presets/main.mbt

@@ -0,0 +1,27 @@
+fn main {
+  let config = @lib.with_queue(
+    @lib.with_file_rotation(
+      @lib.file(
+        "preset-example.log",
+        min_level=@lib.Level::Info,
+        target="demo.preset",
+        auto_flush=true,
+      ),
+      256,
+      max_backups=2,
+    ),
+    max_pending=4,
+    overflow=@lib.QueueOverflowPolicy::DropOldest,
+  ) catch {
+    err => {
+      ignore(err)
+      println("invalid preset config")
+      return
+    }
+  }
+
+  let logger = @lib.build_logger(config)
+  logger.info("preset logger ready", fields=[@lib.field("kind", "preset")])
+  ignore(logger.flush())
+  ignore(logger.file_close())
+}

examples/presets/moon.pkg

@@ -0,0 +1,7 @@
+import {
+  "Nanaloveyuki/BitLogger/src" @lib,
+}
+
+options(
+  "is-main": true,
+)