RFC Deprecate non-escapable single quote inside single quote block

feat: Ony can type quotes inside single quote block and has consistency in behavior for escape symbols. This also enables ' to be representable inside ''-strings.

BREAKING CHANGE: If users rely on \' being not an escaped ', their scripts break.

perf: impact

performance none

usability - consistency in learning language and in usage. no need to learn special escape case for single quotes

maintainability - This should be documented as difference to other shells.

code: input

let str1 = '\'' # valid
let str2 = '\' # invalid, because \' does escape

reason: Consistent behavior is important for usability, so cutting off unexpected cases is beneficial.

context: For arcane reasons the compatibility was not broken in other shells and you end up with quirks like echo $'I\'m a linux admin.', if you want strings with ' included.

behavior of bash/dash/zsh/fish/oil
bash,dash,zsh and oil does not escape ' inside ''-environment
fish does escape ' inside ''-environment