[docs] InstagramBridge: adapt bridge documentation to new documentation structure (#2538)

docs/10_Bridge_Specific/Instagram.md

@@ -0,0 +1,45 @@
+InstagramBridge
+===============
+
+To somehow bypass the [rate limiting issue](https://github.com/RSS-Bridge/rss-bridge/issues/1891)
+it is suggested to deploy a private RSS-Bridge instance that uses a working Instagram account.
+
+Configuration
+-------------
+
+1. Retreiving session id.
+The following steps describe how to get the session id using a Chromium-based browser.
+
+- Create an Instagram account, that you will use for your RSS-Bridge instance.
+It is NOT recommended to use your existing account that is used for common interaction with Instagram services.
+
+- Login to Instagram
+
+- Open DevTools by pressing F12
+
+- Open "Networks tab"
+
+- In the "Filter" field input "i.instagram.com"
+
+- Click on "Fetch/XHR"
+
+- Refresh web page
+
+- Click on any item from the table of http requests
+
+- In the new frame open the "Headers" tab and scroll to "Request Headers"
+
+- There will be a cookie param will lots of `<key>=<value>;` text. You need the value of the "sessionid" key. Copy it.
+
+2. Configuring RSS-Bridge
+
+- In config.ini.php add following configuration:
+
+```
+[InstagramBridge]
+session_id = %sessionid from step 1%
+cache_timeout = %cache timeout in seconds%
+```
+
+The bigger the cache_timeout value, the smaller the chance for RSS-Bridge to throw 429 errors.
+Default cache_timeout is 3600 seconds (1 hour).