Version 0.5.1

• Update doc
• Improved code structure

MMKV has been packaged as android aar lib and uploaded to the maven repository.
Import it in gradle directly like this:

dependencies {
    implementation("net.yangkx:mmkv:0.5.1")
    // Or another one with encryption feature
    // implementation("net.yangkx:mmkv-encrypt:0.5.1")
}

Crate address: https://crates.io/crates/mmkv

Full Changelog: 0.5.0...0.5.1