Add configurable retry logic

Fixes #1382

nitter.example.conf

@@ -34,6 +34,8 @@ proxyAuth = ""
 apiProxy = ""                # nitter-proxy host, e.g. localhost:7000
 disableTid = false           # enable this if cookie-based auth is failing
 maxConcurrentReqs = 2        # max requests at a time per session to avoid race conditions
+maxRetries = 1               # max number of retries on rate limit errors
+retryDelayMs = 150           # delay in ms between retries
 
 # Change default preferences here, see src/prefs_impl.nim for a complete list
 [Preferences]