Adding jvm implementation, but it's broken in lazysodium-java, so will need more work

multiplatform-crypto-libsodium-bindings/src/commonMain/kotlin/com.ionspin.kotlin.crypto/util/LibsodiumRandom.kt

@@ -0,0 +1,36 @@
+package com.ionspin.kotlin.crypto.util
+
+/**
+ * Created by Ugljesa Jovanovic
+ * ugljesa.jovanovic@ionspin.com
+ * on 27-Sep-2020
+ */
+expect object LibsodiumRandom {
+
+    /**
+     * The randombytes_buf() function fills size bytes starting at buf with an unpredictable sequence of bytes.
+     */
+    fun buf(size: Int) : UByteArray
+
+    /**
+     * The randombytes_buf_deterministic function stores size bytes into buf indistinguishable from random bytes without knowing seed.
+     * For a given seed, this function will always output the same sequence. size can be up to 2^31 (~8GB) because we use kotlin arrays
+     * and they are limited by Int primitive type
+     * seed is randombytes_SEEDBYTES bytes long.
+     * This function is mainly useful for writing tests, and was introduced in libsodium 1.0.12. Under the hood, it uses the ChaCha20 stream cipher.
+     *
+     */
+    fun bufDeterministic(size: Int, seed: UByteArray) : UByteArray
+
+    /**
+     * The randombytes_random() function returns an unpredictable value between 0 and 0xffffffff (included).
+     */
+    fun random() : UInt
+
+    /**
+     * The randombytes_uniform() function returns an unpredictable value between 0 and upper_bound (excluded). Unlike r
+     * andombytes_random() % upper_bound, it guarantees a uniform distribution of the possible output values even when
+     * upper_bound is not a power of 2. Note that an upper_bound < 2 leaves only a single element to be chosen, namely 0
+     */
+    fun uniform(upperBound : UInt) : UInt
+}