Redesign base16 Github theme

https://github.com/primer/github-syntax-light/blob/master/lib/github-light.css

src/palettes/base16/_base16-github.scss

-/* Github by Defman21 */
+/* Github by Github, gadenbuie */
 /* rs-theme-is-dark: FALSE */
 
-$base00: #ffffff;
-$base01: #f5f5f5;
-$base02: #c8c8fa;
-$base03: #969896;
-$base04: #e8e8e8;
-$base05: #333333;
-$base06: #ffffff;
-$base07: #ffffff;
-$base08: #ed6a43;
-$base09: #0086b3;
-$base0A: #795da3;
-$base0B: #183691;
-$base0C: #183691;
-$base0D: #795da3;
-$base0E: #a71d5d;
-$base0F: #333333;
+$base00: #fafbfc;
+$base01: #f6f8fa;
+$base02: #D3DAE3;
+$base03: #959da5;
+$base04: #6a737d;
+$base05: #0366D6;
+$base06: #586069;
+$base07: #24292e;
+$base0C: #d73a49;
+$base09: #735c0f;
+$base0A: #6f42c1;
+$base0B: #22863a;
+$base08: #b31d28;
+$base0D: #e36209;
+$base0E: #032f62;
+$base0F: #005cc5;