add symbol comment for pack

docs/02.getting_started.md

@@ -83,6 +83,7 @@ If you experience any problems or have some thoughts on how to improve heavy mak
 ## Known Limitations
 
 * Many objects do not take control signals on their left inlet. `[osc~]` for instance always requires the use of `[sig~]` before connecting a value.
+* Heavy does not support symbols in `[pack]`. e.g. `[pack s f]`.
 * Heavy does not support numbers in `[unpack]`, e.g. `[unpack 0 0]` gives `Heavy only supports arguments 'f' and 's' to unpack.` Workaround is to use `f` instead, e.g. `[unpack f f]`, and if necessary prime the default values with a `[loadbang]` and `[0 0(`.
 * Heavy does not accept arguments and control connections to: `[rzero~]`, `[rzero_rev~]`, `[czero~]`, `[czero_rev~]`. In Heavy, these objects accept only signal inputs. Arguments and control connections are ignored.
 * On the `[select]` object it is currently not possible to set the arguments via the right inlet (internally a hardcoded switch_case is used).