Added Spresense to Downloads

_board/spresense.md

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+---
+layout: download
+board_id: "spresense"
+title: "Spresense Download"
+name: "Spresense"
+manufacturer: "Sony"
+board_url: "https://developer.sony.com/develop/spresense/docs/introduction_en.html"
+board_image: "spresense.jpg"
+features:
+  - Camera connector
+  - GPS Antenna
+---
+
+The Spresense project consists of a Arduino compatible board with Sony’s high performance CXD5602 micro-controller. The CXD5602 has built-in GPS and high-resolution audio capabilities.
+
+The main board uses a processor developed by Sony for IoT and sensing applications. The main board can be operated alone or with the extension board.
+
+The Spresense uses Sony’s new chipset on the main board: * The CXD5602 System on Chip (SoC) multi core processor with GNSS * The CXD5247 power management and audio analog interface chip
+
+The Spresense extension board is a board which extends the interfaces compared to the Spresense main board. The Spresense main board and the Spresense extension board are connected by a Board-to-Board (B-2-B) connector. The Spresense extension board has Arduino Uno pin compatible shape and pin socket locations. However, there are some differences compared to the Arduino Uno. 
+
+## Purchase
+
+* [Sony](https://developer.sony.com/develop/spresense/)
+
+## Contribute
+
+Have some info to add for this board? Edit the source for this page [here](https://github.com/adafruit/circuitpython-org/edit/master/_board/{{ page.board_id }}.md).