docs: dev-manual: common-tasks: highlight creating your own layer is not required

Three's been some feedback saying that people actually missed that
paragraph and thought creating the layer by hand was the only way to do
it instead of leveraging bitbake-layers create-layer tool.

Let's try to make it a bit more obvious one does not need to create the
layer by hand by putting the paragraph into a note.

(From yocto-docs rev: 2b171d267ae37d467f8437c4739f32e5253049b3)

Signed-off-by: Quentin Schulz <foss@0leil.net>
Reviewed-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/dev-manual/common-tasks.rst

@@ -24,15 +24,17 @@ section in the Yocto Project Overview and Concepts Manual.
 Creating Your Own Layer
 -----------------------
 
-It is very easy to create your own layers to use with the OpenEmbedded
-build system, as the Yocto Project ships with tools that speed up creating
-layers. This section describes the steps you perform by hand to create
-layers so that you can better understand them. For information about the
-layer-creation tools, see the
-":ref:`bsp-guide/bsp:creating a new bsp layer using the \`\`bitbake-layers\`\` script`"
-section in the Yocto Project Board Support Package (BSP) Developer's
-Guide and the ":ref:`dev-manual/common-tasks:creating a general layer using the \`\`bitbake-layers\`\` script`"
-section further down in this manual.
+.. note::
+
+   It is very easy to create your own layers to use with the OpenEmbedded
+   build system, as the Yocto Project ships with tools that speed up creating
+   layers. This section describes the steps you perform by hand to create
+   layers so that you can better understand them. For information about the
+   layer-creation tools, see the
+   ":ref:`bsp-guide/bsp:creating a new bsp layer using the \`\`bitbake-layers\`\` script`"
+   section in the Yocto Project Board Support Package (BSP) Developer's
+   Guide and the ":ref:`dev-manual/common-tasks:creating a general layer using the \`\`bitbake-layers\`\` script`"
+   section further down in this manual.
 
 Follow these general steps to create your layer without using tools: