Created Privacy settings (markdown)

Privacy-settings.md

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+There are three "types" (keys) of privacy settings, which are separate from each other:
+* Last seen (also affects whether you can see the other person's)
+* Chat invite (whether you can be added to groups)
+* Phone calls (who can call you)
+
+For each of these, you have 3 modes (rules):
+* All telegram users
+* Your contacts only
+* Nobody
+
+To set any of these, you need a key to work on and a list of values, which will be a global rule, such as `InputPrivacyValueAllowAll` and exceptions, such as allowing or disallowing specific users.
+
+### Last seen example
+
+To allow no one except "@best_friend" to see your last seen, you would use this:
+```python
+from telethon import TelegramClient
+from telethon.tl.functions.account import SetPrivacyRequest
+from telethon.tl.types import InputPrivacyKeyStatusTimestamp, InputPrivacyValueAllowUsers, InputPrivacyValueDisallowAll
+
+client = TelegramClient(session, api_id, api_hash).start()
+bff = client.get_input_entity('@best_friend')
+
+key = InputPrivacyKeyStatusTimestamp()  # working with last seen privacy
+
+rule = InputPrivacyValueDisallowAll()  # main rule is to disallow everyone
+exceptions = InputPrivacyValueAllowUsers([bff])  # more people can be allowed
+values = [rule, exceptions]
+
+client(SetPrivacyRequest(key, values))
+```