Dot-Env Packed v2.0.0

Rework on v1:

• Fresh base code with same idea.
• New integrated: dotenv-flow. Old: dotenv, dotenv-expand, dotenv-conversion.
• parseEnv and getEnv functions are removed.
• New pack function:
  • Has the same idea of the old parseEnv function.
  • Its return value has two properties: parsed and get.
    • parsed is on object which has the same idea of what the old parseEnv function returns.
    • get is a function that has the same idea of the old getEnv function.
• Preload feature is added.