Add troubleshooting guide

troubleshooting.md

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+# Troubleshooting Guide
+
+At first, determine the case: whether the Clairvoyance doesn't work at all, with particular website or stops working during its executing. After this, refer to appropriate section for guidance.
+
+## The Clairvoyance doesn't work at all
+ - Installation: make sure that there were no errors during installation and that you are using correct version of dependencies.
+ - Internet: make sure that you have a stable connection and that the Clairvoyance has rights to access your target.
+ - Usage: refer to the [README](README.md) for usage instructions.
+
+## The Clairvoyance doesn't work with particular website
+ - Scope: make sure that there is no general issue: try `clairvoyance https://rickandmortyapi.com/graphql -o schema.json` or known working target.
+ - URI: check endpoint URI validity (it might be a typo, an erroneous copy or other issue).
+ - Authorization issue: ensure usage of correct headers, cookies and other authorization pieces.
+ - WAF: ensure that the program imitates browser/web client at sufficient level, e.g. check that user agent matches modern browser/app-specific web client.
+
+## The Clairvoyance worked, but stopped working
+ - Does the program work when you restart it? If the answer is yes, check "Rate Limits", if not, then check "Server-related issue"
+ - Rate Limits: server might rate limit requests from the same IP/user. Lower amount of threads or try to run the program in a slow mode
+ - Server-related issue: server might be temporary unavailable, check the endpoint manually using browser or other previously used tools. Alternatively, your IP/user might have been banned.