Use mode: history on the vue-router by using a SPA hack for Github Pages

[zebateira]

This PR implements a hack that enables non-hashing routing to github-pages-powered websites. It's working locally in dev and production mode.

Hack can be found here: https://github.com/rafrex/spa-github-pages

SEO Note from the repo:

A quick SEO note - while it's never good to have a 404 response, it appears based on Search Engine Land's testing that Google's crawler will treat the JavaScript window.location redirect in the 404.html file the same as a 301 redirect for its indexing. From my testing I can confirm that Google will index all pages without issue, the only caveat is that the redirect query is what Google indexes as the url. For example, the url example.tld/about will get indexed as example.tld/?p=/about. When the user clicks on the search result, the url will change back to example.tld/about once the site loads.

closes #388, #105
Will enable us to start working on: #258

[zebateira]

Let's revisit this later when we can say for sure all the implications of this are tackled.
For now the main issue to fix is the 404 Github page.