Use the latest builds on Windows and validate versions

• Fixes #10
• Validate the versions available on Windows by having a list of versions and URLs from the RubyInstaller website.

Use a newer OpenSSL for Ruby 2.3

• Using OpenSSL 1.0.2u instead of OpenSSL 1.0.2q for Ruby 2.3 Ubuntu & macOS builds.
  See eregon/ruby-build#1 and rbenv/ruby-build#1397.

• Ruby >= 2.4 Ubuntu & macOS use the system OpenSSL.

Add TruffleRuby 19.3.1

v1.5.0

Add TruffleRuby 19.3.1

Support all Ruby versions between 2.3.0 and 2.7.0

That's 33 versions in total.

Read from .ruby-version if no version is set

Implements #4.

Add support for Windows

v1.2.0

Better error if MSYS2 is missing

Support short version syntax

Implements #1

First stable release

v1.0.0

Fill action.yml