Use regconfig in sort parse_websearch to prevent out of order results

[paradoxxxzero]

Fixes #75

[alext]

I've also just hit this issue. This fix resolves it for me.

I found while testing that using ts_rank_cd with a query parsed with the pg_catalog.simple regconfig (the default in the 1-argument version of parse_websearch) was always returning 0, meaning the results were returned in an arbitrary order.