Shell parser/AST for POSIX/Bash/mksh/zsh, in TypeScript

feat: add lazy parseStmtsSeq and parseWordsSeq iterators master

Mirrors mvdan/sh's \`Parser.StmtsSeq\` and \`Parser.WordsSeq\` (added in v3.11.0/v3.12.0). \`parseStmtsSeq\` yields top-level statements as they parse; \`parseWordsSeq\` yields words from an argv-style stream. Both sit in src/seq.ts on top of new \`Parser.statementsSeq()\` / \`Parser.wordsSeq()\` generators.