Update 'Performance'

Performance.md

@@ -1 +1,38 @@
-TODO
+On my dated system with dual Intel(R) Xeon(R) E5-2670 v2 CPUs, the `translate()` function can process one word every 227.462 nanoseconds on average.
+I tested this by feeding the words_alpha.txt file from <https://github.com/dwyl/english-words> to anslatetray-file 10 times, calculating the average runtime,
+and dividing by 370105 (the number of words in the file). The times do not including loading from and writing to the disk.
+
+Note that raw calls to `translate_word()` would be faster, but `translate()` has to be smart enough to preserve symbols and whitespace surrounding each word, while still accounting for contractions and other edge-cases.
+
+```
+> for run in {1..10}; do anslatetray-file words_alpha.txt words_alpha_pig_latin.txt; done
+Sucessful: took 90144337ns to translate
+Sucessful: took 82581222ns to translate
+Sucessful: took 82803035ns to translate
+Sucessful: took 80643452ns to translate
+Sucessful: took 80542962ns to translate
+Sucessful: took 81848295ns to translate
+Sucessful: took 81600103ns to translate
+Sucessful: took 86463460ns to translate
+Sucessful: took 87399299ns to translate
+Sucessful: took 87821022ns to translate
+```
+
+There are also some benchmarks built into the library that you can run to easily check the performance of it on your system:
+
+```
+> cargo bench --features nightly-features
+[...]
+test translate_strings::benches::translate_ferb_lorem_ipsum            ... bench:      11,284 ns/iter (+/- 331)
+test translate_strings::benches::translate_ferb_project_description    ... bench:       1,852 ns/iter (+/- 28)
+test translate_strings::benches::translate_lorem_ipsum                 ... bench:      11,033 ns/iter (+/- 284)
+test translate_strings::benches::translate_project_description         ... bench:       1,848 ns/iter (+/- 61)
+test translate_strings::benches::translate_yay_lorem_ipsum             ... bench:      10,968 ns/iter (+/- 263)
+test translate_strings::benches::translate_yay_project_description     ... bench:       1,809 ns/iter (+/- 40)
+test translate_words::benches::translate_word_ferb_the_word_translator ... bench:         120 ns/iter (+/- 3)
+test translate_words::benches::translate_word_the_word_translator      ... bench:         126 ns/iter (+/- 7)
+test translate_words::benches::translate_word_yay_the_word_translator  ... bench:         121 ns/iter (+/- 6)
+[...]
+```
+
+Anslatortray is quite fast, but it could be faster :). Both the speed and the quality of translation are priorities for me, and I'm working to improve them both!