add README

README.md

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+# Kotlin KDF
+
+This library provides various [Key Derivation Function](https://en.wikipedia.org/wiki/Key_derivation_function)
+implementations in Kotlin Multiplatform.
+
+## Features
+
+* [PBKDF2](https://en.wikipedia.org/wiki/PBKDF2)
+* Multiplatform support
+    * JVM
+    * JavaScript
+    * Native (Linux)
+
+## Installation
+
+Add the following to your `build.gradle.kts`.
+
+```kotlin
+repositories {
+    maven("https://git.infendro.com/api/packages/Infendro/maven")
+}
+
+dependencies {
+    implementation("com.infendro:kdf:1.0.3")
+}
+```
+
+## Usage
+
+```kotlin
+import com.infendro.hash.SHA256
+import com.infendro.kdf.PBKDF2
+
+fun main() {
+    // create a PBKDF2 instance using HMAC SHA256
+    val kdf = PBKDF2(SHA256)
+
+    // securely hash value with some salt
+    //   this example uses 100_000 iterations and 32 bytes of length
+    val value = "password".encodeToByteArray()
+    val salt = "...".encodeToByteArray()
+    val hash = kdf.hash(value, salt, 100_000, 32)
+}
+```