[FR] Support specifying weights

[NightMachinery]

E.g.,

echo "1 normal choice
1.2 another somewhat normal choice
3 important choice
100 super critical choice" | fzy --read-weights='^(\d+(\.\d*)?)\s'

would multiply whatever score these candidates got by their weights. One result would be that super critical choice would probably stay at the top if its score is anything but zero.

This has multiple applications, among which is having MRU (most recently used) weights that help used choices get to the top.