Remove unneeded extern crates

Closes GH-28.

Co-authored-by: Bernhard Berger <bernhardberger3456@gmail.com>

Author: Hocdoc

Untitled.txt

@@ -6,7 +6,6 @@ micromark.js: `atLineEnding` in html (text) should always eat arbitrary whitespa
 ```rs
 // ---------------------
 // Useful helper:
-extern crate std;
 use std::println;
 use alloc::string::String;
 

benches/bench.rs

@@ -1,6 +1,4 @@
-#[macro_use]
-extern crate criterion;
-use criterion::{BenchmarkId, Criterion};
+use criterion::{criterion_group, criterion_main, BenchmarkId, Criterion};
 use std::fs;
 
 fn readme(c: &mut Criterion) {

build.rs

@@ -1,4 +1,3 @@
-extern crate reqwest;
 use regex::Regex;
 use std::fs;
 
@@ -67,7 +66,6 @@ async fn commonmark() {
 // > 👉 **Important**: this module is generated by `build.rs`.
 // > It is generate from the latest CommonMark website.
 
-extern crate markdown;
 use markdown::{{to_html_with_options, CompileOptions, Options}};
 use pretty_assertions::assert_eq;
 

examples/lib.rs

@@ -1,5 +1,3 @@
-extern crate markdown;
-
 fn main() -> Result<(), String> {
     // Turn on debugging.
     // You can show it with `RUST_LOG=debug cargo run --example lib`

fuzz/fuzz_targets/markdown.rs

@@ -1,14 +1,10 @@
 #![no_main]
 use libfuzzer_sys::fuzz_target;
-extern crate markdown;
 
 fuzz_target!(|data: &[u8]| {
     if let Ok(s) = std::str::from_utf8(data) {
         let _ = markdown::to_html(s);
-        let _ = markdown::to_html_with_options(
-            s,
-            &markdown::Options::gfm()
-        );
+        let _ = markdown::to_html_with_options(s, &markdown::Options::gfm());
         let _ = markdown::to_mdast(s, &markdown::ParseOptions::default());
         let _ = markdown::to_mdast(s, &markdown::ParseOptions::gfm());
     }

readme.md

@@ -1236,7 +1236,6 @@ impl Options {
 
 #[cfg(test)]
 mod tests {
-    extern crate std;
     use super::*;
     use crate::util::mdx::Signal;
     use alloc::format;

src/configuration.rs

@@ -1,5 +1,3 @@
-extern crate alloc;
-
 use alloc::{str::FromStr, string::String};
 
 /// Type of line endings in markdown.
@@ -82,7 +80,6 @@ impl FromStr for LineEnding {
 
 #[cfg(test)]
 mod tests {
-    extern crate std;
     use super::*;
 
     #[test]

src/util/line_ending.rs

@@ -1,5 +1,3 @@
-extern crate alloc;
-
 use alloc::string::String;
 
 /// Signal used as feedback when parsing MDX ESM/expressions.
@@ -89,7 +87,6 @@ pub type ExpressionParse = dyn Fn(&str, &ExpressionKind) -> Signal;
 
 #[cfg(test)]
 mod tests {
-    extern crate std;
     use super::*;
     use alloc::boxed::Box;
 

src/util/mdx.rs

@@ -1,4 +1,3 @@
-extern crate markdown;
 use markdown::{
     mdast::{Emphasis, Node, Paragraph, Root, Strong, Text},
     to_html, to_html_with_options, to_mdast,