initial support for pca10059

Using the official USB Vendor name even for other boards.

targets/pca10059.json

@@ -0,0 +1,6 @@
+{
+	"inherits": ["nrf52840"],
+	"build-tags": ["pca10059"],
+	"linkerscript": "targets/pca10059.ld",
+	"flash-command": "nrfutil pkg generate --hw-version 52 --sd-req 0x0 --application {hex} --application-version 1 /tmp/tinygo_$$.zip && nrfutil dfu usb-serial -pkg /tmp/tinygo_$$.zip -p {port} -b 115200 && rm -f /tmp/tinygo_$$.zip"
+}

targets/pca10059.ld

@@ -0,0 +1,10 @@
+
+MEMORY
+{
+    FLASH_TEXT (rw) : ORIGIN = 0x00001000, LENGTH = 0xDF000
+    RAM (xrw)       : ORIGIN = 0x20000008, LENGTH = 0x3FFF8
+}
+
+_stack_size = 2K;
+
+INCLUDE "targets/arm.ld"