Add custom generators thru tool_requires docs

reference/extensions/custom_generators.rst

@@ -5,7 +5,7 @@ Custom Conan generators
 
 In the case that you need to use a build system or tool that is not supported by Conan
 off-the-shelf, you could create your own custom integrations using a custom generator.
-This can be done in two different ways.
+This can be done in three different ways.
 
 Custom generators as python_requires
 ------------------------------------
@@ -98,3 +98,47 @@ argument:
 .. code-block:: bash
 
     conan install --requires=zlib/1.2.13 -g MyGenerator
+
+
+Generators from tool_requires
+-----------------------------
+
+.. include:: ../../common/experimental_warning.inc
+
+A direct dependency tool requires can also be used to provide custom generators.
+The following example shows how to create a custom generator that generates a file with the
+dependencies of the package, just like the example above, but using a ``tool_require`` instead of a ``python_require``
+to inject the generator into the recipe, by adding them to the ``self.generators_info`` list inside the ``package_info`` method.
+
+.. code-block:: python
+    :caption: mygenerator/conanfile.py
+
+    from conan import ConanFile
+    from conan.tools.files import save
+
+    class MyGenerator:
+        def __init__(self, conanfile):
+            self._conanfile = conanfile
+
+        def generate(self):
+            deps_info = ""
+            for dep, _ in self._conanfile.dependencies.items():
+                deps_info = f"{dep.ref.name}, {dep.ref.version}"
+            save(self._conanfile, "deps.txt", deps_info)
+
+    class MyToolReq(ConanFile):
+        name = "mygenerator-tool"
+        version = "1.0"
+
+        def package_info(self):
+            self.generators_info.append(MyGenerator)
+
+And then having a ``tool_requires`` in your recipe for the ``mygenerator-tool`` package will automatically
+inject the generator into the recipe.
+
+.. note::
+
+    Note that built-in generators can also be injected using tool_requires,
+    by adding them by name: ``self.generators_info.append("CMakeDeps")``.
+    ``tool_require``ing this package will inject the ``CMakeDeps`` generator into the recipe
+    just as if it was declared in its ``generators`` attribute.