Created Environment Variables (markdown)

Environment-Variables.md

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+# ytdl_write_config
+
+If set to "true", this will override any config items if its associated environment variable is set as well.
+
+For example, if this environment variable is enabled and the environment variable `ytdl_use_local_db` is set to "false", on startup the config item "use_local_db" will be set to false.
+
+See a list of config items and their [associated environment variables here](https://github.com/Tzahi12345/YoutubeDL-Material/wiki/Configuration#items).
+
+# ALLOW_CONFIG_MUTATIONS
+
+This is an environment variable for the `node-config` dependency we use. Due to a bug discovered where the config file couldn't be modified on Docker, this was added to fix that. It does not affect any functionality, but removing it may cause errors.