Define intentions to support RISC-V arch. (#53)

On behalf of #51

README.md

@@ -44,7 +44,7 @@
 * `ppcle_64` - if the value is `ppc64le`
 * `s390_32` - if the value is `s390`
 * `s390_64` if the value is `s390x`
-
+* `riscv` if the value is `riscv`
 Note: The bitness part of this property relies on the bitness of the JVM binary, e.g. You'll get the property that ends with `_32` if you run a 32-bit JVM on a 64-bit OS.
 
 #### Property: `os.detected.bitness`