QuickInstall support (#94)

See this issue: https://github.com/alsuren/cargo-quickinstall/issues/27

Quick Install is a hosted repo of built crates, essentially. The approach I've taken here is
a list of strategies:

1. First, we check the crate meta or default and build the URL to the repo. Once we have
   that, we perform a `HEAD` request to the URL to see if it's available.
2. If it's not, we build the URL to the quickinstall repo, and perform a `HEAD` to there.

As soon as we've got a hit, we use that. I've built it so it's extensible with more strategies.
This could be useful for #4.

This also adds a prompt before downloading from third-party sources, and logs a short
name for a source, which is easier to glance than a full URL, and includes a quick refactor
of the install/link machinery.

src/fetchers/quickinstall.rs

@@ -0,0 +1,80 @@
+use std::path::Path;
+
+use log::info;
+use reqwest::Method;
+
+use super::Data;
+use crate::{download, remote_exists, PkgFmt};
+
+const BASE_URL: &str = "https://github.com/alsuren/cargo-quickinstall/releases/download";
+const STATS_URL: &str = "https://warehouse-clerk-tmp.vercel.app/api/crate";
+const USER_AGENT: &str = concat!(env!("CARGO_PKG_NAME"), "/", env!("CARGO_PKG_VERSION"));
+
+pub struct QuickInstall {
+    package: String,
+}
+
+#[async_trait::async_trait]
+impl super::Fetcher for QuickInstall {
+    async fn new(data: &Data) -> Result<Box<Self>, anyhow::Error> {
+        let crate_name = &data.name;
+        let version = &data.version;
+        let target = &data.target;
+        Ok(Box::new(Self {
+            package: format!("{crate_name}-{version}-{target}"),
+        }))
+    }
+
+    async fn check(&self) -> Result<bool, anyhow::Error> {
+        let url = self.package_url();
+        self.report().await?;
+        info!("Checking for package at: '{url}'");
+        remote_exists(&url, Method::HEAD).await
+    }
+
+    async fn fetch(&self, dst: &Path) -> Result<(), anyhow::Error> {
+        let url = self.package_url();
+        info!("Downloading package from: '{url}'");
+        download(&url, dst).await
+    }
+
+    fn pkg_fmt(&self) -> PkgFmt {
+        PkgFmt::Tgz
+    }
+
+    fn source_name(&self) -> String {
+        String::from("QuickInstall")
+    }
+    fn is_third_party(&self) -> bool {
+        true
+    }
+}
+
+impl QuickInstall {
+    fn package_url(&self) -> String {
+        format!(
+            "{base_url}/{package}/{package}.tar.gz",
+            base_url = BASE_URL,
+            package = self.package
+        )
+    }
+
+    fn stats_url(&self) -> String {
+        format!(
+            "{stats_url}/{package}.tar.gz",
+            stats_url = STATS_URL,
+            package = self.package
+        )
+    }
+
+    pub async fn report(&self) -> Result<(), anyhow::Error> {
+        info!("Sending installation report to quickinstall (anonymous)");
+        reqwest::Client::builder()
+            .user_agent(USER_AGENT)
+            .build()?
+            .request(Method::HEAD, &self.stats_url())
+            .send()
+            .await?;
+        Ok(())
+    }
+}