* feat: support pipe splitting

BREAKING CHANGE: `p.halt()` should be replaced with `$({halt: true})`, stdio defaults to `pipe`

* test: add delayed `pipe()` test

* feat: add `pid` getter to `ProcessPromise`

* test: check chainable pipe literals

* test: kill nc process on end

* refactor!: remove `halt()` method

* refactor: remove runner logic from getters

* fix: enhance `Shell` result type

* chore: bring back `halt` method to avoid breaking change

* style: improve `Options` block formatting

* perf: improve cmd formatter

* chore: update internal reexports

* chore: up build deps

* chore(deps): update which to v5.0.0

* fix: properly promisify pipe stream args

* test: extend Duplex pipe test asserts

* refactor: simplify `promisifyStream` helper

* chore: bump version to 8.2.0

* test: check stream as stdio input

* build: replace fx with node

* chore: shrink a few bytes

* ci: remove redundand script

* test: refactor npm pack test

* test: refactor copyright test

continues #921