Update DIRECTORY.md [skip actions]

Author: vil02

DIRECTORY.md

@@ -101,6 +101,8 @@
  * [Subset Generation](https://github.com/TheAlgorithms/Rust/blob/master/src/dynamic_programming/subset_generation.rs)
  * [Trapped Rainwater](https://github.com/TheAlgorithms/Rust/blob/master/src/dynamic_programming/trapped_rainwater.rs)
  * [Word Break](https://github.com/TheAlgorithms/Rust/blob/master/src/dynamic_programming/word_break.rs)
+ * Financial
+ * [Present Value](https://github.com/TheAlgorithms/Rust/blob/master/src/financial/present_value.rs)
  * General
  * [Convex Hull](https://github.com/TheAlgorithms/Rust/blob/master/src/general/convex_hull.rs)
  * [Fisher Yates Shuffle](https://github.com/TheAlgorithms/Rust/blob/master/src/general/fisher_yates_shuffle.rs)