[FIX] Correctly escape data-wovnio attribute in snippet

[torkelbe]

Purpose/goal of Pull Request (Issue #)

Correctly escape data-wovnio attribute in the widget snippet when using fallback method.

Comments

wovnrb's fallback method is currently inserting a snippet that is incorrectly escaped twice like this

<script src="//j.wovn.io/1" async="true" data-wovnio="key=Gl5Niu&amp;amp;backend=true&amp;amp;currentLang=en&amp;amp;defaultLang=en&amp;amp;urlPattern=path&amp;amp;langCodeAliases={}&amp;amp;version=WOVN.rb_2.0.1" data-wovnio-type="fallback_snippet">

With this change, the content of data-wovnio will only be escaped once, like this

<script src="//j.wovn.io/1" async="true" data-wovnio="key=Gl5Niu&amp;backend=true&amp;currentLang=en&amp;defaultLang=en&amp;urlPattern=path&amp;langCodeAliases={}&amp;version=WOVN.rb_2.0.1" data-wovnio-type="fallback_snippet">

'Readline' for breakpoint debugging

This PR also adds the rb-readline gem, which we now need for breakpoint debugging.