Third-party source for Stolo Node firmware 0.3.1 (SenseCAP T1000-E)

These are the exact board-support and library sources compiled into
stolo-t1000e-firmware-0.3.1.zip, as installed by `make prep-t1000e` in the
firmware source (stolo-node-firmware-0.3.1-source.tar.gz):

  Seeeduino-nrf52-1.1.13/   Seeeduino:nrf52 board package 1.1.13: the core
                            (LGPL-2.1, with FreeRTOS, Nordic nrfx and the Arm
                            nRF MDK inside), the SenseCAP T1000-E variant and
                            the six libraries the firmware uses (SPI,
                            Adafruit_LittleFS, InternalFileSytem,
                            Bluefruit52Lib, Adafruit_nRFCrypto,
                            Adafruit_TinyUSB_Arduino)
  arduino-libraries/Crypto-0.4.0/   the Arduino "Crypto" library 0.4.0

Each directory keeps its own licence files. NOTICES.txt, published next to
the firmware, collects the licences that apply to the binary.

To rebuild the firmware with these sources instead of downloading them, put
Seeeduino-nrf52-1.1.13 where arduino-cli keeps the Seeeduino:nrf52 1.1.13
platform (packages/Seeeduino/hardware/nrf52/1.1.13) and Crypto-0.4.0 in
your Arduino libraries folder, then run `make firmware-stolo-t1000e` in the
firmware source.

Not included, because they are generally available and used unmodified as
build tools: the GNU Arm Embedded Toolchain 9-2019-q4 (GCC, binutils, and
the newlib 3.1.0 C library it links in; source at developer.arm.com and
sourceware.org/newlib) and Arm CMSIS 5.7.0 (Apache-2.0, github.com/ARM-software/CMSIS_5).
