examples: Add the component manager example

examples/build_system/cmake/component_manager/CMakeLists.txt

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+# For more information about build system see
+# https://docs.espressif.com/projects/esp-idf/en/latest/api-guides/build-system.html
+# The following five lines of boilerplate have to be in your project's
+# CMakeLists in this exact order for cmake to work correctly
+cmake_minimum_required(VERSION 3.5)
+
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+project(component_manager)

examples/build_system/cmake/component_manager/README.md

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+# Using the component manager for downloading dependencies
+
+This example demonstrates how to use [IDF Component Manager](https://pypi.org/project/idf-component-manager/) for downloading dependencies from [the component registry](https://components.espressif.com). More details and use cases of IDF Component Manager can be found in the programming guide under `API Guides` -> `Tools` -> `IDF Component Manager`.
+
+## How to use the example
+### Hardware Required
+
+This example is designed to work with any commonly available development kit.
+
+### Build and Flash
+
+Run `idf.py reconfigure` to configure this project. During CMake execution the component manager will process data from the manifest file `./main/idf_component.yml` where 2 dependencies are defined:
+
+- `idf: ">=4.1"` - Specifies required version of ESP-IDF.
+- `example/cmp: ">=3.3.3"` - Defines dependency on [example/cmp](https://components.espressif.com/component/example/cmp) component that is used by the main component.
+
+CMake Output:
+```
+...
+Solving dependencies requirements
+Updating lock file at /home/user/esp-idf/examples/build_system/cmake/component_manager/dependencies.lock
+Processing 2 dependencies:
+[1/2] example/cmp
+[2/2] idf
+...
+```
+
+Content of the `./managed_components` directory after successful build:
+```
+> find  ./managed_components
+./managed_components
+./managed_components/example__cmp
+./managed_components/example__cmp/include
+./managed_components/example__cmp/include/cmp.h
+./managed_components/example__cmp/LICENSE
+./managed_components/example__cmp/README.md
+./managed_components/example__cmp/CMakeLists.txt
+./managed_components/example__cmp/changelog.md
+./managed_components/example__cmp/cmp.c
+./managed_components/example__cmp/idf_component.yml
+```
+
+Flash the project and run the serial monitor to view the output:
+
+```
+idf.py -p PORT flash monitor
+```
+
+### Example Output
+
+The example outputs a line from the `cmp_hello` function from the component downloaded by the component manager.
+
+```
+Hello from example component!
+```

examples/build_system/cmake/component_manager/main/CMakeLists.txt

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+idf_component_register(SRCS "component_manager.c"
+                    INCLUDE_DIRS ".")

examples/build_system/cmake/component_manager/main/component_manager.c

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+#include <stdio.h>
+#include "cmp.h"
+
+void app_main(void)
+{
+    cmp_hello();
+}

examples/build_system/cmake/component_manager/main/idf_component.yml

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+dependencies:
+  # Required IDF version
+  idf: ">=4.1"
+
+  # Defining a dependency from the registry:
+  # https://components.espressif.com/component/example/cmp
+  example/cmp: ">=3.3.3"
+
+  # # Other ways to define dependencies
+  #
+  # # For components maintained by Espressif only name can be used.
+  # # Same as `espressif/cmp`
+  # component: "~1.0.0"
+  #
+  # # Or in a longer form with extra parameters
+  # component2:
+  #   version: ">=2.0.0"
+  #
+  #   # For transient dependencies `public` flag can be set.
+  #   # `public` flag doesn't have an effect for the `main` component.
+  #   # All dependencies of `main` are public by default.
+  #   public: true
+  #
+  #   # For components hosted on non-default registry:
+  #   service_url: "https://componentregistry.company.com"
+  #
+  # # For components in git repository:
+  # test_component:
+  #   path: test_component
+  #   git: ssh://git@gitlab.com/user/components.git
+  #
+  # # For test projects during component development
+  # # components can be used from a local directory
+  # # with relative or absolute path
+  # some_local_component:
+  #   path: ../../projects/component