feat(splitByCase): add whitespace as a string splitter character

[Eazash]

Partially fixes #95 and #92 (marking as partial fixes as they also exhibit the issue in #101)

Resolves #96

splitByCase has inconsistent behaviour when dealing with whitespaces. Adding whitespace as a separator character fixes these issues, which are also causing the inconsistent spacing behavior in titleCase

A few things to note

• This PR refactors string-splitter checks to use a regex so as to ensure all other whitespaces are captured
• Since using a regex was not practical in types.ts, this PR uses an enumerated list of whitespace characters from fix(titleCase): insert extra space when convert valid string #97 by @ntnyq-dev

console.log(`${JSON.stringify(splitByCase("FOO BAR"))} -- ${titleCase("FOO BAR")}`) 
console.log(`${JSON.stringify(splitByCase("foo bar"))} -- ${titleCase("foo bar")}`) 
console.log(`${JSON.stringify(splitByCase("foO bar"))} -- ${titleCase("foO bar")}`) 

/** Before **/
// ["FO","O ","BAR"] -- FO O  BAR
// ["foo bar"] -- Foo bar
// ["fo","O bar"] -- Fo O bar

/** After **/
// ["FOO","BAR"] -- FOO BAR
// ["foo","bar"] -- Foo Bar
// ["fo","O","bar"] -- Fo O Bar

Based on both #98 and #97 🫡