Update copyright year and version

Signed-off-by: Still Hsu <5843208+Still34@users.noreply.github.com>

docs/docfx.json

@@ -51,7 +51,7 @@
     "overwrite": "_overwrites/**/**.md",
     "globalMetadata": {
       "_appTitle": "Discord.Net Documentation",
-      "_appFooter": "Discord.Net (c) 2015-2019 2.1.1",
+      "_appFooter": "Discord.Net (c) 2015-2020 2.2.0",
       "_enableSearch": true,
       "_appLogoPath": "marketing/logo/SVG/Logomark Purple.svg",
       "_appFaviconPath":  "favicon.ico"