fix: bridge nested PlatformIO async dependencies

tools/platformio/dependencies.py

@@ -0,0 +1,24 @@
+"""Expose WiFiManager's async dependencies to PlatformIO's nested library builds."""
+from __future__ import print_function
+
+import glob
+import os
+
+from SCons.Script import Import
+
+Import("env")
+
+
+def append_dependency_include(package_prefix):
+    """Add the installed package's source directory when PlatformIO has it."""
+    package_root = env.subst("$PROJECT_LIBDEPS_DIR")
+    candidates = glob.glob(os.path.join(package_root, package_prefix + "*", "src"))
+    if candidates:
+        env.Append(CPPPATH=[candidates[0]])
+
+
+append_dependency_include("ESPAsyncWebServer")
+if env.subst("$PIOPLATFORM") == "espressif8266":
+    append_dependency_include("ESPAsyncTCP")
+elif env.subst("$PIOPLATFORM") == "espressif32":
+    append_dependency_include("AsyncTCP")