Add react rails

[aabdaab]

This small PR sets up react-rails gem to use React for more interactive widgets like Bubble Chart.
Read README for more info but long story short, that allows us to create react components in app/javascript/components and use them in erb files like so:

<%= react_component("HelloWorld", { greeting: "Hello from react-rails." }) %>

The first argument being component's name and second being props. HelloWorld added for demonstration.

I also added the number of companies in the center of the PieChart (not ideally styled yet) /tpi/sectors - check here

[rapzo]

Must we do it The Rails Way™? We could achieve the same with a PWA imho.
Personal preference, is all.

[simaob]

given the time pressure I'd go with something we know already and are comfortable with. Reduce the risks as much as possible.

[aabdaab]

The Rails Way was precisely what I wanted to avoid 😅 That's why I added react-rails, what do you mean exactly?

[tsubik]

Ok, let's do BubbleChart component with some default text for now instead of HelloWorld one.

[aabdaab]

@tsubik done 👍

[tsubik]

You can also remove that hello_react pack.

[aabdaab]

done

[simaob]

lgtm =)