provide a way to order menu links

[zmalik]

What would you like to be added:
Some control over the menu links order for runbooks so we can group related docs together like runbooks or release notes above

Why is this needed:
To provide a better UX for users when navigating docs for an operator

[zmalik]

cc: @gerred for visibility

[porridge]

FTR, the current ordering is a total hack that attempts to put the install document first, but otherwise the ordering is alphabetical.

@meichstedt had an idea to control this using frontmatter weight. Perhaps this will be possible once we move to GatsbyJS?