ci: Improve link checker conditions

Link checker excludes checks on local links and links with variables.

Signed-off-by: Songqian Li <sionli@tencent.com>

.lychee.toml

@@ -14,8 +14,16 @@ exclude = [
 
     # OSDev has added bot protection and accesses my result in 403 Forbidden.
     '^https://wiki.osdev.org',
+    # Exclude all pages with $ in the URL since $XXX is a variable
+    "\\$.*",
+    # Exclude local files
+    "file://.*",
 ]
 
+# Exclude loopback addresses
+exclude_loopback = true
+
+
 max_retries = 3
 
 retry_wait_time = 5