fix: escape ampersand in ProxyCommand

Fixes #479.

Author: kylecarbs

src/main/kotlin/com/coder/gateway/util/Escape.kt

@@ -12,8 +12,10 @@ fun escape(s: String): String {
     if (s.contains("\n")) {
         throw Exception("argument cannot contain newlines")
     }
-    if (s.contains(" ") || s.contains("\t")) {
-        return "\"" + s.replace("\"", "\\\"") + "\""
+    if (s.contains(" ") || s.contains("\t") || s.contains("&")) {
+        // See https://github.com/coder/jetbrains-coder/issues/479
+        // Escape existing " and &
+        return "\"" + s.replace("\"", "\\\"").replace("&", "\\&") + "\""
     }
     return s.replace("\"", "\\\"")
 }