Merge pull request #2877 from jimmylism/update_button_contrast

Update dark mode button to have better contrast

src/ogs.styl

@@ -298,7 +298,7 @@ dark.toast-fg                           = dark.bg
 dark.link-color                         = #539bff
 dark.link-color-active                  = darken(dark.link-color, 20%)
 
-dark.default-button                     = lighten(dark.bg, 10%)
+dark.default-button                     = lighten(dark.bg, 20%)
 dark.default-button-color               = dark.fg
 dark.primary                            = darken(light.primary, core-color-darken-amount)
 dark.danger                             = darken(light.danger, core-color-darken-amount)