Import ESP_UniClock (upstream 1189810)

Vendored from https://github.com/gpeter62/ESP_UniClock: the sketch
source, the web UI and the libraries the ESP8266 build needs, unpacked
from the bundled zips. Adds a PlatformIO project for the ESP-12. The
source is unchanged; local changes follow as separate commits.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

firmware/uniclock/lib/ArduinoJson/extras/tests/JsonDocument/nesting.cpp

@@ -0,0 +1,30 @@
+// ArduinoJson - https://arduinojson.org
+// Copyright © 2014-2022, Benoit BLANCHON
+// MIT License
+
+#include <ArduinoJson.h>
+#include <catch.hpp>
+
+TEST_CASE("JsonDocument::nesting()") {
+  DynamicJsonDocument doc(4096);
+
+  SECTION("return 0 if uninitialized") {
+    REQUIRE(doc.nesting() == 0);
+  }
+
+  SECTION("returns 0 for string") {
+    JsonVariant var = doc.to<JsonVariant>();
+    var.set("hello");
+    REQUIRE(doc.nesting() == 0);
+  }
+
+  SECTION("returns 1 for empty object") {
+    doc.to<JsonObject>();
+    REQUIRE(doc.nesting() == 1);
+  }
+
+  SECTION("returns 1 for empty array") {
+    doc.to<JsonArray>();
+    REQUIRE(doc.nesting() == 1);
+  }
+}