upd(website): Update Slack to Discord

According to TSC voting we are migrating to Discord.
All links and content need to be updated accordingly.

Signed-off-by: Denys Fedoryshchenko <[email protected]>

Author: nuclearcat

kernelci.org/config.toml

@@ -68,10 +68,10 @@ footer_about_disable = false
   desc = "Development takes place here!"
 
 [[params.links.developer]]
-  name = "Slack"
-  url = "http://kernelci.slack.com/"
-  icon = "fab fa-slack"
-  desc = "Chat with other project developers"
+  name = "Discord"
+  url = "https://discord.gg/KWbrbWEyqb"
+  icon = "fab fa-discord"
+  desc = "Chat with other developers!"
 
 # -- custom main menu --
 

kernelci.org/content/en/org/maintainers.md

@@ -242,13 +242,13 @@ price plan.
 
 * Maintainers: `broonie`, `khilman`, `padovan`
 
-### Slack
+### Discord
 
-The [KernelCI Slack channel](https://kernelci.slack.com) may be used as an
-alternative to IRC.  However, more people are using IRC so Slack is only there
+The [KernelCI Discord channel](https://discord.gg/KWbrbWEyqb) may be used as an
+alternative to IRC.  However, more people are using IRC so Discord is only there
 to facilitate communication when IRC is not practical.
 
-* Maintainers: `khilman`, `spbnick`
+* Maintainers: `khilman`, `spbnick`, `padovan`
 
 ### Twitter