Escape path for live reload. Fix #1247. (#1266)

zola serve's live reload feature used to fail on Windows due to the path
separator (`\`) to not being escaped.

Cargo.lock

@@ -3270,6 +3270,7 @@ dependencies = [
  "notify",
  "open",
  "relative-path",
+ "serde_json",
  "site",
  "termcolor",
  "tokio",

Cargo.toml

@@ -36,6 +36,7 @@ ctrlc = "3"
 open = "1.2"
 globset = "0.4"
 relative-path = "1"
+serde_json = "1.0"
 
 site = { path = "components/site" }
 errors = { path = "components/errors" }

src/cmd/serve.rs

@@ -153,13 +153,13 @@ fn rebuild_done_handling(broadcaster: &Sender, res: Result<()>, reload_path: &st
                     r#"
                 {{
                     "command": "reload",
-                    "path": "{}",
+                    "path": {},
                     "originalPath": "",
                     "liveCSS": true,
                     "liveImg": true,
                     "protocol": ["http://livereload.com/protocols/official-7"]
                 }}"#,
-                    reload_path
+                    serde_json::to_string(&reload_path).unwrap()
                 ))
                 .unwrap();
         }