using of Sync api

[ehsan2003]

Describe the bug A clear and concise description of what the bug is. In nodejs ( and generally javascript) we should avoid using Sync api but used in : https://github.com/alik0211/mtproto-core/blob/master/envs/node/pbkdf2.js#L4

Expected behavior the module should not block the event loop by using Sync api, instead it should use callback or promise / async-await syntax

Context:

• Library environment: node
• Library version: 6.2.0
• Node version (if node environment): x.x.x
• Browser version (if browser environment): x.x.x