provide README files with pointers to the developer info for plugins

also add a paragraph with information about the ML-PACE plugin to the
plugin developer info docs.

doc/src/Developer_plugins.rst

@@ -276,10 +276,27 @@ Compilation of the plugin can be managed via both, CMake or traditional
 GNU makefiles.  Some examples that can be used as a template are in the
 ``examples/plugins`` folder.  The CMake script code has some small
 adjustments to allow building the plugins for running unit tests with
-them. Another example that converts the KIM package into a plugin can be
+them.
-found in the ``examples/kim/plugin`` folder.  No changes to the sources
+
-of the KIM package themselves are needed; only the plugin interface and
+Another example that converts the KIM package into a plugin can be found
-loader code needs to be added.  This example only supports building with
+in the ``examples/kim/plugin`` folder.  No changes to the sources of the
-CMake, but is probably a more typical example. To compile you need to
+KIM package themselves are needed; only the plugin interface and loader
-run CMake with -DLAMMPS_SOURCE_DIR=<path/to/lammps/src/folder>.  Other
+code needs to be added.  This example only supports building with CMake,
+but is probably a more typical example. To compile you need to run CMake
+with -DLAMMPS_SOURCE_DIR=<path/to/lammps/src/folder>.  Other
 configuration setting are identical to those for compiling LAMMPS.
+
+A second example for a plugin from a package is in the
+``examples/PACKAGES/pace/plugin`` folder that will create a plugin from
+the ML-PACE package.  In this case the bulk of the code is in a static
+external library that is being downloaded and compiled first and then
+combined with the pair style wrapper and the plugin loader.  This
+example also contains a NSIS script that can be used to create an
+Installer package for Windows (the mutual licensing terms of the
+external library and LAMMPS conflict when distributing binaries, so the
+ML-PACE package cannot be linked statically, but the LAMMPS headers
+required to build the plugin are also available under a less restrictive
+license).  This will automatically set the required environment variable
+and launching a (compatible) LAMMPS binary will load and register the
+plugin and the ML-PACE package can then be used as it was linked into
+LAMMPS.

doc/utils/sphinx-config/false_positives.txt

@@ -2369,6 +2369,9 @@ Nord
 norder
 Nordlund
 normals
+normx
+normy
+normz
 Noskov
 noslip
 noticable

examples/PACKAGES/pace/plugin/README.txt

@@ -0,0 +1,2 @@
+This folder contains a loader and support files to build the ML-PACE package as plugin.
+For more information please see: https://docs.lammps.org/Developer_plugins.html

examples/kim/plugin/README.txt

@@ -0,0 +1,2 @@
+This folder contains a loader and support files to build the KIM package as plugin.
+For more information please see: https://docs.lammps.org/Developer_plugins.html