create_trie creates a trie (a key-value store optimised
for matching) out of a provided character vector of keys, and a numeric,
character, logical or integer vector of values (both the same length).
trie(keys, values)a `trie` object.
trie_add and trie_remove for adding to and removing
from tries after their creation, and longest_match and other match functions
for matching values against the keys of a created trie.
# An integer trie
int_trie <- trie(keys = "foo", values = 1)
# A string trie
str_trie <- trie(keys = "foo", values = "bar")