[Global] Implement the nav bar

[kptdobe]

On each blog entry, there is a nav bar allowing to navigate from one entry to another (time based). It includes the time to read (?) and the share feature (we should skip the social features - like and feed).

[MarquiseRosier]

I'll take this @davidnuescheler , may I have access to make PR's :)

[davidnuescheler]

tracked some more detail in #2

[rofe]

I think this issue is about a different "nav bar"than #2:

It's a tool bar appearing when you scroll down on a blog post, allowing to navigate to the next newer or older post, and showing an approximate read time.

I don't know if we even need to implement this, and I would definitely not prioritize this for the pitch. Instead, let's focus on the issues with the pitch label...

[davidnuescheler]

ah, cool. well, so i'll leave it alone...