updated readme uwu!

README.md

@@ -2,14 +2,32 @@ fif
 ===
 [![Crates.io](https://img.shields.io/crates/v/fif.svg?style=flat-square)](https://crates.io/crates/fif)
 [![Crates.io](https://img.shields.io/crates/l/fif.svg?style=flat-square)](https://git.bune.city/lynnesbian/fif/src/branch/master/LICENSE)
+![Minimum Supported Rust Version](https://img.shields.io/badge/msrv-1.43.0-orange?style=flat-square)
 
 A command-line tool for detecting and optionally correcting files with incorrect extensions.
 
 ## Installation
+### Default backend
 ```bash
 cargo install --locked fif
 ```
 
+### Other backends
+`fif` supports using [infer](https://crates.io/crates/infer) or [xdg-mime](https://crates.io/crates/xdg-mime) as its
+backend for looking up file types. By default, xdg-mime will be used on Linux, and infer on all other systems.
+
+xdg-mime should work on any Unixy system with [libmagic/file(1)](https://www.darwinsys.com/file/) installed, although
+I've only tested it on Linux. infer should work on any system.
+
+You can override the default backend for your system at compile time like so:
+
+```bash
+# xdg-mime
+cargo install --features=xdg-mime-backend
+# infer
+cargo install --features=infer-backend
+```
+
 ## Usage
 See `fif --help` for more.
 
@@ -34,3 +52,5 @@ You might find it useful to output this script to a file (rather than to stdout)
 ```bash
 fif -E images ~/Pictures > output.sh
 ```
+
+More coming soon!