fix: use strict comparison with undefined

feat: now the frontend is more similar to the one within kite.koboldai.net; when digiting within the input field it's possible to fire the funtion pressing enter

doc: rename customTokenize() to customWordPunctTokenize(), update some docstrings

test: rename test cases to test the embedded stemmer

feat: add optional embedded stemmer

doc: add docstrings to js functions, rewrite them as classic function instead then arrow function

feat: improve compatibility with lite.koboldai.net

refactor: rename occurrences of WordFreq to WordsFreq

refactor: rename occurrences of "word frequency" to "words frequency"

fix: update misleading html id and aria labels

feat: add output table filtering, sorting and ordering

doc: add missing docstrings to js functions

feat: refactor frontend, improve css style

feat: add a basic js frontend