logging: backend: websocket: Add missing header file

The log_backend_ws.h include file was missing which caused
build issues.

Fixes #80392

Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>

include/zephyr/logging/log_backend_ws.h

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_LOG_BACKEND_WS_H_
+#define ZEPHYR_LOG_BACKEND_WS_H_
+
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Register websocket socket where the logging output is sent.
+ *
+ * @param fd Websocket socket value.
+ *
+ * @return 0 if ok, <0 if error
+ */
+int log_backend_ws_register(int fd);
+
+/**
+ * @brief Unregister websocket socket where the logging output was sent.
+ *
+ * @details After this the websocket output is disabled.
+ *
+ * @param fd Websocket socket value.
+ *
+ * @return 0 if ok, <0 if error
+ */
+int log_backend_ws_unregister(int fd);
+
+/**
+ * @brief Get the websocket logger backend
+ *
+ * @details This function returns the websocket logger backend.
+ *
+ * @return Pointer to the websocket logger backend.
+ */
+const struct log_backend *log_backend_ws_get(void);
+
+/**
+ * @brief Start the websocket logger backend
+ *
+ * @details This function starts the websocket logger backend.
+ */
+void log_backend_ws_start(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_LOG_BACKEND_WS_H_ */