Increase blacksmith cache TTL to one month

Author: Kobzol

blacksmith/src/main.rs

@@ -8,7 +8,7 @@ use mdbook::{
 use mdbook_blacksmith::Blacksmith;
 
 const CACHE_FILE: &str = ".blacksmith-cache.json";
-const CACHE_TTL_SECONDS: u64 = 3600; // 1 hour
+const CACHE_TTL_SECONDS: u64 = 3600 * 24 * 30; // 1 month
 
 fn main() {
     // If RUST_LOG is present use that, else default to info level printing.