* Added sizes and alignments to WASI docs

* Fixed formatting

* Made requested changes

* Fixed whitespace issues

* Fixed up whitespace one last time

- New proposal process updates.
 - witx planning
 - Update on the module-types linking proposal.

This commit fixes links in `fd_readdir` description/docs which were
using an outdated (now invalid) ref syntax when referencing `dirent`
struct.

The changes apply to docs only and only to `wasi_unstable` and
`wasi_snapshot_preview1` snapshots. The `wasi_ephemeral` has properly
referenced links.

* Document why there is no path_filestat_set_size

* Address review feedback.

* Rephrase the rationale

This commit fixes an outdated ref syntax when referencing back to
`event` struct.

…OSIX (WebAssembly#257)

* Techinically speaking, preadv and pwritev are not in POSIX.

Ref: https://pubs.opengroup.org/onlinepubs/9699919799/idx/ip.html

* Document about atomicity of `write` and `pwrite`

Related thread of ZULIP: https://bytecodealliance.zulipchat.com/#narrow/stream/219900-wasi/topic/Why.20is.20.60iovecs.60.20an.20array.20of.20strings.3F

The thread refers atomicity of `read`, but I couldn't make a good expression
for the atomicity of `read`.
So I add document only in `write` and `pwrite`.

* Limit the scope of atomicity

The related POSIX document refers only to threads. https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_09_07

So the atomicity is limited in the process

* Fix test

* Fix after review

WebAssembly#257 (comment)

The atomicity is guaranteed only for regular files or symbolic links (only symbolic links for a regular files, right?)

Delete expressions indicating 'all or nothing' to reflect the actual behavior of POSIX's`write` etc.

* Fix after review

WebAssembly#257 (comment)

Delete the sentences related to 'all data' completely

Don't refer to symlink

* Fix after review

WebAssembly#257 (review)

)

Perhaps this is a temporary fix. We'll have to update the link again after the design of the module types gets updated.

* Elaborate on the definitions of commands and reactors.

This pulls out the parts of WebAssembly#281 which document existing practice.

* Simplify the text about __heap_base and __data_end.

We no longer need to say "applications may export these", but it's still
useful to say that environments shouldn't access them.

Also add the meeting notes for the last few meetings.

* witx: add AsRef implementation to witx::Id

* witx: add PartialEq implementations for Id

* Fix link in phases/README.md

* Update link to docs/Process

* witx: update wast dependency to 20.0.0

* bump witx crate version to 0.8.6

* witx: bump wast dependency to 22.0.0

* witx: bump crate version to 0.8.7

…bly#320)

In accordance with this advisory it's recommended we move to a
different scheme of setting env vars and updating PATH:

https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/

This fixes the Markdown links so at least they display correctly. However, there are several link issues:
 - https://github.com/WebAssembly/wasi-misc does not exist
 - https://github.com/WebAssembly/wasi-io does not exist
 - https://github.com/WebAssembly/wasi-classic-command may not be the correct link for wasi-command-line
 - https://github.com/proxy-wasm/spec is the correct link for this project but is not a repo containing WITX

…embly#339)

There are several discussions going about character encodings and
strings across different forums. This presentation will summarize
the current conversations and discuss the high-level pros and cons
of various options being discussed.

See notes for [2020-10-22 subgroup meeting](https://github.com/WebAssembly/WASI/blob/master/meetings/2020/WASI-10-22.md)

As discussed in WebAssembly#329 (comment), this change creates a landing page explaining roughly what you get in each of the documentation pages and moves the helpful links from the main README to this page.

This updates the agenda from 11-05 which didn't happen due to meeting
logistics, and adds another link for the case insensitivity discussion.

the idea here was to enable handles to have a subtyping hierarchy,
but this isnt compatible with wasm extern refs and we never used it
anywhere, so its safe to delete all this code.

Fixes WebAssembly#356

…y#367)

* Add the `(@WitX noreturn)` annotation to proc_exit

The noreturn annotation was invented solely for the sake of proc_exit,
but we never actually used it in the spec documents.

This annotation sets the `noreturn` bit in the `InterfaceFunc` struct.
Downstream tools are free to do with that bit what they will.

* bugfix: witx rendering

* bnump witx version to 0.8.8

Following the organization sketched out here:

WebAssembly#360

This PR adds several new directories and starts a work-in-progress
make-snapshot.sh script for creating snapshots.

The `phases` directory is not yet removed; that can happen once
we've transitioned everything to the new organization.