Issue trustin#61. Added riscv64 support

Signed-off-by: alex <zigmatulin@gmail.com>

README.md

@@ -45,6 +45,7 @@
 * `s390_32` - if the value is `s390`
 * `s390_64` if the value is `s390x`
 * `riscv` if the value is `riscv`
+* `riscv64` if the value is `riscv64`
 * `e2k` if the value is `e2k`
 
 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.

src/main/java/kr/motd/maven/os/Detector.java

@@ -248,6 +248,9 @@ private static String normalizeArch(String value) {
         if ("riscv".equals(value)) {
             return "riscv";
         }
+        if ("riscv64".equals(value)) {
+            return "riscv64";
+        }
         if ("e2k".equals(value)) {
             return "e2k";
         }