docs: resolve ambiguity issue for `X-Ass-Timeoffset` (resolves #152)

.github/README.md

@@ -235,7 +235,9 @@ If you need to override a specific part of the config to be different from the g
 | **`X-Ass-Domain`** | Override the domain returned for the clipboard (useful for multi-domain hosts) |
 | **`X-Ass-Access`** | Override the generator used for the resource URL. Must be one of: `original`, `zws`, `gfycat`, `random`, or `timestamp` ([see above](#access-types)) |
 | **`X-Ass-Gfycat`** | Override the length of Gfycat ID's. Defaults to `2` |
-| **`X-Ass-Timeoffset`** | Override the timestamp offset. Defaults to `UTC+0` |
+| **`X-Ass-Timeoffset`** | Override the timestamp offset. Defaults to `UTC+0`. Available options are whatever [Luxon] accepts (for example: `America/Edmonton` or `UTC-7`) |
+
+[Luxon]: https://moment.github.io/luxon/#/zones?id=specifying-a-zone
 
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