Update SPI.adoc (#889)

Added endTransaction() link to function section.

Author: John-Karatka

Language/Functions/Communication/SPI.adoc

@@ -39,6 +39,7 @@ To read more about Arduino and SPI, you can visit the https://docs.arduino.cc/le
 link:../spi/spisettings[SPISettings] +
 link:../spi/begin[begin()] +
 link:../spi/begintransaction[beginTransaction()] +
+link:../spi/endtransaction[endTransaction()] +
 link:../spi/end[end()] +
 link:../spi/setbitorder[setBitOrder()] +
 link:../spi/setclockdivider[setClockDivider()] +