doc: update Zephyr features list in intro

Intro page update to list the features and major changes that
happened in the last year

fixes #5136

Signed-off-by: David B. Kinder <david.b.kinder@intel.com>

doc/introduction/introducing_zephyr.rst

@@ -14,7 +14,8 @@ boards can be found :ref:`here <boards>`.
 Licensing
 *********
 
-Zephyr uses the `Apache 2.0 license`_ (as found in the LICENSE file in the
+Zephyr is permissively licensed using the `Apache 2.0 license`_
+(as found in the ``LICENSE`` file in the
 project's `GitHub repo`_).  There are some
 imported or reused components of the Zephyr project that use other licensing,
 as described in :ref:`Zephyr_Licensing`.
@@ -31,35 +32,48 @@ Distinguishing Features
 The Zephyr kernel offers a number of features that distinguish it from other
 small-footprint OSes:
 
-#. **Single address-space**. Combines application-specific code
+**Single address-space**
+   Combines application-specific code
    with a custom kernel to create a monolithic image that gets loaded
    and executed on a system's hardware. Both the application code and
    kernel code execute in a single shared address space.
 
-#. **Highly configurable**. Allows an application to incorporate *only*
+**Highly configurable / Modular for flexibility**
+   Allows an application to incorporate *only*
    the capabilities it needs as it needs them, and to specify their
    quantity and size.
 
-#. **Compile-time resource definition**. Allows system resources
-   to be defined at compile-time, which reduces code size and
-   increases performance.
+**Cross Architecture**
+   Supports a wide variety of :ref:`supported boards<boards>` with different CPU
+   architectures and developer tools. Contributions have added support
+   for an increasing number of SoCs, platforms, and drivers.
 
-#. **Minimal error checking**. Provides minimal runtime error checking
+**Compile-time resource definition**
+   Allows system resources
+   to be defined at compile-time, which reduces code size and
+   increases performance for resource-limited systems.
+
+**Minimal error checking**
+   Provides minimal runtime error checking
    to reduce code size and increase performance. An optional error-checking
    infrastructure is provided to assist in debugging during application
    development.
 
-#. **Extensive suite of services**. Offers a number of familiar services
-   for development:
+**Extensive suite of services**
+   Offers a number of familiar services for development:
 
-   * *Multi-threading Services* for priority-based, non-preemptive and
-     preemptive threads with optional round robin time-slicing.
+   * *Multi-threading Services* for cooperative, priority-based,
+     non-preemptive, and preemptive threads with optional round robin
+     time-slicing.  Includes pthreads compatible API support.
 
    * *Interrupt Services* for compile-time registration of interrupt handlers.
 
    * *Memory Allocation Services* for dynamic allocation and freeing of
      fixed-size or variable-size memory blocks.
 
+   * *Memory Protection* wtih architecture-specific stack-overflow protection,
+     kernel object and device driver permission tracking, and thread isolation.
+
    * *Inter-thread Synchronization Services* for binary semaphores,
      counting semaphores, and mutex semaphores.
 
@@ -69,6 +83,27 @@ small-footprint OSes:
    * *Power Management Services* such as tickless idle and an advanced idling
      infrastructure.
 
+   * *Native Networking Stack* fully featured and optimized, including
+     LwM2M and BSD sockets compatible support. OpenThread support is also
+     provided - a mesh network designed to securely and reliably
+     connect hundreds of products around the home.
+
+   * *Bluetooth Low Energy* 5.0 support including a Bluetooth
+     qualification-ready BLE controller, and BLE Mesh.
+
+   * *File system* with Newtron Flash Filesystem (NFFS) and FAT
+     support, and file system enhancements for logging and
+     configuration.
+
+   * *Native Linux, macOS, and Windows Development* with command-line
+     Cmake build environment. A native POSIX port, letting you build and
+     run Zephyr as a native application on Linux and other OSes aids
+     development and testing.
+
+   * *ZTest infrastructure* and a coverage test suite for continuous
+     integration testing and verification as features are added and updated.
+
+
 .. include:: ../../README.rst
    :start-after: start_include_here