Add something like Roadmap or Porting Status or Progress

[Kirillpt]

The idea is to help contributors see current progress, for example what methods have already been ported.

There is some example of progress document:

Progress (propose your name)

Array

• .first
• .last
• .max
• .min
• .join
• .size

Enum

• .all?
• .count
• .each
• .map
• .reduce
• .select

File

• .write

Hash

• .compact
• .dig!
• .dig
• .fetch_values
• .fetch_with
• .fetch
• .get
• .keys
• .merge
• .put
• .reject
• .select
• .slice!
• .slice
• .transform_keys
• .transform_values
• .values_at
• .values

String

• .split
• .concat

etc