Add examples and expand README for release

examples/HelloPlaceholder/src/main.cpp

@@ -0,0 +1,51 @@
+#include <Arduino.h>
+#include <TemplateEngine.h>
+
+namespace {
+
+static String deviceName = "DFTE Getting Started";
+static String buildId    = "v1.0.0";
+
+const char SIMPLE_TEMPLATE[] = R"TPL(
+Device: %DEVICE_NAME%
+Build: %BUILD_ID%
+
+DFTE lets you reuse this template across Serial, HTTP, or any other transport.
+)TPL";
+
+const char* getDeviceName() { return deviceName.c_str(); }
+const char* getBuildId()    { return buildId.c_str(); }
+
+}  // namespace
+
+void setup() {
+  Serial.begin(115200);
+  while (!Serial) { /* wait for USB CDC */ }
+
+  Serial.println();
+  Serial.println(F("=== DFTE Hello Placeholder ==="));
+
+  PlaceholderRegistry registry;
+  registry.registerRamData("%DEVICE_NAME%", getDeviceName);
+  registry.registerRamData("%BUILD_ID%", getBuildId);
+
+  TemplateContext ctx;
+  ctx.setRegistry(&registry);
+  TemplateRenderer::initializeContext(ctx, SIMPLE_TEMPLATE, false);
+
+  uint8_t buffer[64];
+  while (!TemplateRenderer::isComplete(ctx) && !TemplateRenderer::hasError(ctx)) {
+    size_t written = TemplateRenderer::renderNextChunk(ctx, buffer, sizeof(buffer));
+    if (!written) {
+      break;
+    }
+    Serial.write(buffer, written);
+  }
+
+  Serial.println(F("\nRendering complete."));
+}
+
+void loop() {
+  // Nothing else to do in the basic example.
+}
+