feat: use EJS on html files, inject process.env.* vars

[Kocal]

Q	A
Bug fix?	no
New feature?	yes
Tests pass?	yes
Fixed tickets	~

In order to load Vue Devtools remote <script> (#334 (comment)) only for development environment, a good solution is to use a condition (with EJS) on HTML files.

That means you can write:

<% if (NODE_ENV === 'development') { %>
<script src="http://localhost:8098"></script>
<% } %>