chore: add readme/license

Author: TerrorJack

LICENSE

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+MIT License
+
+Copyright (c) Tweag I/O Limited.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# `pandoc-wasm`
+
+[![Chat on Matrix](https://matrix.to/img/matrix-badge.svg)](https://matrix.to/#/#haskell-wasm:matrix.terrorjack.com)
+
+The latest version of `pandoc` CLI compiled as a standalone
+`wasm32-wasi` module that can be run by engines like `wasmtime` as
+well as browsers.
+
+## [Live demo](https://tweag.github.io/pandoc-wasm)
+
+Stdin on the left, stdout on the right, command line arguments at the
+bottom. No convert button, output is produced dynamically as input
+changes.
+
+You're also more than welcome to fetch the
+[`pandoc.wasm`](https://tweag.github.io/pandoc-wasm/pandoc.wasm)
+module and make your own customized app. `pandoc.wasm` is fully
+`wasm32-wasi` compliant and doesn't make use of any JSFFI feature in
+the ghc wasm backend.
+
+## Building
+
+`pandoc.wasm` is built with 9.12 flavour of ghc wasm backend in CI,
+which can be installed via
+[`ghc-wasm-meta`](https://gitlab.haskell.org/ghc/ghc-wasm-meta). You
+need at least 9.10 since it's the earliest major version with (my
+non-official) backports for ghc wasm backend's Template Haskell & ghci
+support.
+
+It's built using my
+[fork](https://github.com/TerrorJack/pandoc/tree/wasm) which is based
+on latest `pandoc` release and patches dependencies, cabal config as
+well as some module code to make things compilable to wasm:
+
+- No http client/server functionality. `wasip1` doesn't have proper
+  sockets support anyway, and support for future versions of wasi is
+  not on my radar for now.
+- No lua support. lua requires `setjmp`/`longjmp` which already work
+  in `wasi-libc` to some extent, but that requires wasm exception
+  handling feature which is not supported by `wasmtime` yet.
+
+Other functionalities should just work, if not feel free to file a bug
+report :)
+
+## Acknowledgements
+
+Thanks to John MacFarlane and all the contributors who made `pandoc`
+possible: a fantastic tool that has benefited many developers and is a
+source of pride for the Haskell community!
+
+Thanks to all past efforts of using `asterius` to compile `pandoc` to
+wasm, including but not limited to:
+
+- George Stagg's [`pandoc-wasm`](https://github.com/georgestagg/pandoc-wasm)
+- Yuto Takahashi's [`wasm-pandoc`](https://github.com/y-taka-23/wasm-pandoc)
+- My legacy asterius pandoc [demo](https://asterius.netlify.app/demo/pandoc/pandoc.html)