Create discord-filter.txt

Add ad-block filter list.
- Filters telemetry as well as additional client trackers.

discord-filter.txt

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+! Title: Discord Privacy Filter
+! Expires: 7 days
+! Description: Block tracking endpoints on Discord without impacting usability.
+! Homepage: https://fem.git.lgbt/wry/no-discord-tracking
+! License: MIT; https://fem.mint.lgbt/wry/no-discord-tracking/raw/LICENSE
+! Version: 1.0.0
+
+!! Telemetry:
+
+! Old telemetry endpoint that is no longer used.
+||discord.com/api/*/track
+! Used to track every click, menu change, or other interaction on the client.
+! https://luna.gitlab.io/discord-unofficial-docs/science.html.
+||discord.com/api/*/science
+! Block error and crash reporting.
+||discord.com/api/*/metrics
+||discord.com/error-reporting-proxy
+! Block analytics.
+! Note: experimental filter (disabled).
+!  ||discord.com/api/*?with_analytics_token*
+
+!! Other Tracking:
+
+! Prevent sending list of processes to Discord (used for rich presence).
+||discord.com/api/*/applications/detectable
+! Block sending typing indicator in Discord channels.
+||discord.com/api/*/channels/*/typing
+! Block friend suggestions.
+||discord.com/api/*/friend-suggestions
+! Block Cloudflare fingerprinting.
+! https://developers.cloudflare.com/fundamentals/reference/cdn-cgi-endpoint/.
+||discord.com/cdn-cgi