Change crate edition to "2018"

Cargo.toml

@@ -3,7 +3,7 @@ name = "qoi-fast"
 version = "0.2.0"
 description = "VERY fast encoder/decoder for QOI (Quite Okay Image) format"
 authors = ["Ivan Smirnov <rust@ivan.smirnov.ie>"]
-edition = "2021"
+edition = "2018"
 readme = "README.md"
 license = "MIT"
 repository = "https://github.com/aldanor/qoi-fast"

qoi-bench/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "qoi-bench"
 version = "0.1.0"
-edition = "2021"
+edition = "2018"
 
 [dependencies]
 # internal

src/encode.rs

@@ -1,3 +1,4 @@
+use std::convert::TryFrom;
 use std::io::Write;
 
 use crate::consts::{QOI_HEADER_SIZE, QOI_OP_INDEX, QOI_OP_RUN, QOI_PADDING, QOI_PADDING_SIZE};