chore: update docs (#1291)

* chore: structure ISA

* feat: update design and specs

* feat: clean up ISA intro, move PUBLISH to system

* feat: separate ISA docs into extensions

* feat: incorporate user IO section into RV32IM extensions

* feat: separate out phantom sub-instructions

* feat: move native, and add intro links

* feat: clean up native language

* chore: align Poseidon2 opcode names

* feat: remove register and immediate sections

* feat: move syscalls

* feat: explain x0 behavior

* feat: align naming and wording for keccak, sha256, ecc

* chore: align naming of pairing opcode with repo

* feat: compress memory explanation

* feat: explain hints

* feat: update public values description

* feat: more intro edits

* feat: document address space constraints

* fix: replace e by 2 in keccak

* chore: revert extraneous RISCV

* feat: split custom instruction and transpiler pages

* feat: update readme to explain ELF and transpiler

* feat: separate custom instruction format into extensions

* feat: split transpiler format into extensions

* chore: remove syscalls from ISA

* feat: add missing links

* [chore] Mention the new `HintRandom` phantom discriminant in the docs (see PR#1294) (#1296)

* Update ISA.md

* Add a small note to the doc

* feat: update hintstorew and hintbuffer in RISCV

* fix: hintstore and hintbuffer details

* feat: add todos and hintrandom to riscv

* feat: remove unsupported system phantom opcodes

* feat: add hintbuffer, split out RV32IM

* feat: reword x0 language

* feat: explicitly specify x0 handling

* feat: make setup transpilation explicit

* feat: add setup for complex

* feat: update pairing opcodes

* fix: Fp2 -> Fp

* fix: correct ind(rd) definition

* feat: add docs for HintLoad

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Co-authored-by: Golovanov399 <[email protected]>

Author: yi-sun