Refactor code to share logic between ruby-install-builder and windows

* Make use of ruby-installer-versions.js to validate the version on Windows.

ruby-install-builder.js

@@ -0,0 +1,33 @@
+const core = require('@actions/core')
+const io = require('@actions/io')
+const tc = require('@actions/tool-cache')
+const axios = require('axios')
+
+const builderReleaseTag = 'builds-newer-openssl'
+const releasesURL = 'https://github.com/eregon/ruby-install-builder/releases'
+const metadataURL = 'https://raw.githubusercontent.com/eregon/ruby-install-builder/metadata'
+
+export async function getAvailableVersions(engine) {
+  const response = await axios.get(`${metadataURL}/versions.json`)
+  const versions = response.data
+  return versions[engine]
+}
+
+export async function install(platform, ruby) {
+  const rubyPrefix = await downloadAndExtract(platform, ruby)
+  core.addPath(`${rubyPrefix}/bin`)
+  return rubyPrefix
+}
+
+async function downloadAndExtract(platform, ruby) {
+  const rubiesDir = `${process.env.HOME}/.rubies`
+  await io.mkdirP(rubiesDir)
+
+  const url = `${releasesURL}/download/${builderReleaseTag}/${ruby}-${platform}.tar.gz`
+  console.log(url)
+
+  const downloadPath = await tc.downloadTool(url)
+  await tc.extractTar(downloadPath, rubiesDir)
+
+  return `${rubiesDir}/${ruby}`
+}