update logging book

Author: szabgab

books/logging/src/SUMMARY.md

@@ -2,12 +2,14 @@
 
 - [Logging](./index.md)
   - [Getting started with logging in Rust](./getting-started-with-logging.md)
-  - [Simple Logger new](./simple-logger-new.md)
-  - [Simple Logger init](./simple-logger-init.md)
-  - [Simple Logger level](./simple-logger-level.md)
+  - [Simple Logger new](./simple-logger.md)
+    - [Simple Logger new](./simple-logger-new.md)
+    - [Simple Logger init](./simple-logger-init.md)
+    - [Simple Logger level](./simple-logger-level.md)
   - [Logging with log4rs](./logging-with-log4rs.md)
-  - [Simple use of env_logger](./env-logger-demo.md)
-  - [env_logger with Builder](./env-logger-with-builder.md)
+  - [env_logger](./env-logger.md)
+    - [env_logger in a simpl way](./env-logger-demo.md)
+    - [env_logger with Builder](./env-logger-with-builder.md)
 - [Tracing](./tracing.md)
   - [Tracing demo](./tracing-demo.md)
   - [Tracing in a library](./tracing-in-a-library.md)

books/logging/src/env-logger-with-builder.md

@@ -1,5 +1,10 @@
 # env_logger with Builder
 
+Using the `env_logger::Builder` we can define the formatting of each log-line.
+
+We can also set the default log-level, if the user does not set one via the `RUST_LOG` environment variable.
+
+
 {% embed include file="src/examples/logging/env-logger-builder/Cargo.toml" %}
 
 {% embed include file="src/examples/logging/env-logger-builder/src/main.rs" %}

books/logging/src/env-logger.md

@@ -0,0 +1,3 @@
+# env_logger
+
+[env-logger](https://crates.io/crates/env-logger)

books/logging/src/examples/logging/simple_logger_init/Cargo.lock

@@ -3,8 +3,6 @@ name = "simple_logger_init"
 version = "0.1.0"
 edition = "2021"
 
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-
 [dependencies]
 simple_logger = "4.2"
 log = "0.4"