Increase search result prominence for close matches in result titles

[IanButterworth]

I tested this through Chrome's DevTools (breakpoint before the function runs, adding this change, then running the page so that the index is generated with this change)

It makes search queries that closely match the result title rank much higher.
For "Macros" and "Arrays" queries in searching the base docs it makes those sections 1st or 2nd, whereas they're currently way down in the list.

Fixes #631 and #1110

[mortenpi]

LGTM. Thanks, @ianshmean! It will be a short while before this will actually show up on Julia's stable docs (either with 1.3 of 1.4).

[IanButterworth]

@mortenpi I know this is probably frowned upon, but would JuliaLang/docs.julialang.org#9 be acceptable? Seems like this fix would be helpful retroactively

Obviously just a suggestion, as it would break the rules..

[IanButterworth]

Perhaps a sensible approach would be to see how it goes for new releases first before deciding whether to do anything retroactive..