PIP Summary: remove Slack link, add Discord link

PIP/README.md

@@ -1,6 +1,6 @@
 # PascalCoin Improvement Proposals (PIP)
 
-People wishing to submit PIPs, first should discuss their idea on the [PascalCoin Slack](http://pascalcoin.org/slack-self-invite/). 
+People wishing to submit PIPs, first should discuss their idea on the [PascalCoin Discord](https://discordapp.com/invite/sJqcgtD). 
 If they wish to continue, copy [this template](PIP-template.md) and ensure your PIP is in accordance to the [standard](PIP-0001.md). Submit to the PIP Maintainer for publication here.
 
 ## All PIPs