[Doc] Taichi spec: prims, attributes, subscriptions, slicings (#4697)
[Doc] Taichi spec: prims, attributes, subscriptions, slicings (#4697)

* [Doc] Taichi spec: prims, attributes, subscriptions, slicings

* Fix
yuanming-hu/taichi,yuanming-hu/taichi,yuanming-hu/taichi,yuanming-hu/taichi