add sheet manager

modules/bottom-sheet/android/src/main/java/expo/modules/bottomsheet/SheetManager.kt

@@ -0,0 +1,28 @@
+package expo.modules.bottomsheet
+
+import java.lang.ref.WeakReference
+
+class SheetManager {
+  companion object {
+    private val sheets = mutableSetOf<WeakReference<BottomSheetView>>()
+
+    fun add(view: BottomSheetView) {
+      sheets.add(WeakReference(view))
+    }
+
+    fun remove(view: BottomSheetView) {
+      sheets.forEach {
+        if (it.get() == view) {
+          sheets.remove(it)
+          return
+        }
+      }
+    }
+
+    fun dismissAll() {
+      sheets.forEach {
+        it.get()?.dismiss()
+      }
+    }
+  }
+}