trie_add.RdAdds a single word to the trie.
trie_add(trie, word_to_add)
| trie | A   | 
    
|---|---|
| word_to_add | The word to be added in the trie.  | 
    
a logical indicating that if the addition is successful or not. Returns TRUE if word is added successfully Returns FALSE if the word already exists in the trie.
#> [1] TRUE