add option to override locale messages per-group, update readme

src/store/common_config.rs

@@ -7,6 +7,7 @@ use crate::tr::TranslationTable;
 pub struct CommonConfig {
     pub groups_dir: String,
     pub locales_dir: String,
+    pub validate_locales: bool,
     /// Max number of missed notifs to process after connect
     pub max_catchup_notifs: usize,
     /// Max number of missed statuses to process after connect
@@ -36,6 +37,7 @@ impl Default for CommonConfig {
         Self {
             groups_dir: "groups".to_string(),
             locales_dir: "locales".to_string(),
+            validate_locales: true,
             max_catchup_notifs: 30,
             max_catchup_statuses: 50,
             delay_fetch_page_s: 0.25,