Update README.md

Author: fintelia

README.md

@@ -1,2 +1,34 @@
 # image-extras
-Decoding support for additional image formats
+Decoding support for additional image formats beyond those provided by the [`image`](https://crates.io/crates/image) crate.
+
+## Supported formats
+
+| Extension | File Format Description |
+| --------- | -------------------- |
+| PCX | [Wikipedia](https://en.wikipedia.org/wiki/PCX#PCX_file_format) |
+
+## New Formats
+
+We welcome PRs to add support for additional image formats.
+
+#### Required criteria
+
+- [ ] Must be one of the raster image formats recognized by [ImageMagick](https://imagemagick.org/script/formats.php).
+- [ ] No patent or licensing restrictions.
+- [ ] Specification or sufficiently detailed file format description freely available online.
+- [ ] Must include multiple test images with suitable licenses.
+- [ ] Implementation must be entirely in Rust.
+
+#### Additional nice-to-haves
+
+- [ ] Minimal or no dependencies on external libraries.
+- [ ] No use of unsafe code.
+
+## Fuzzing
+
+Fuzzing is not a priority for this crate and decoders may panic or worse on
+malformed input. Please do not open issues for crashes found by fuzzing, though
+PRs fixing them are welcome.
+
+This is an intentional tradeoff to balance the inclusion criteria for new
+formats with maintainer time and effort.