add a .clang-format file (#9154)

src/mqtt/ServiceEnvelope.h

@@ -4,10 +4,10 @@
 
 // meshtastic_ServiceEnvelope that automatically releases dynamically allocated memory when it goes out of scope.
 struct DecodedServiceEnvelope : public meshtastic_ServiceEnvelope {
-    DecodedServiceEnvelope(const uint8_t *payload, size_t length);
-    DecodedServiceEnvelope(DecodedServiceEnvelope &) = delete;
-    DecodedServiceEnvelope(DecodedServiceEnvelope &&);
-    ~DecodedServiceEnvelope();
-    // Clients must check that this is true before using.
-    const bool validDecode;
+  DecodedServiceEnvelope(const uint8_t *payload, size_t length);
+  DecodedServiceEnvelope(DecodedServiceEnvelope &) = delete;
+  DecodedServiceEnvelope(DecodedServiceEnvelope &&);
+  ~DecodedServiceEnvelope();
+  // Clients must check that this is true before using.
+  const bool validDecode;
 };