Add Osaka Jade theme to default theme set. (#514)

* Add Osaka Jade Theme

* Use jpg for bg for lower size with no quality difference

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Co-authored-by: Justin Lowry <j.lowry@hey.com>
Co-authored-by: David Heinemeier Hansson <david@hey.com>

themes/osaka-jade/swayosd.css

@@ -0,0 +1,5 @@
+@define-color background-color #11221C;
+@define-color border-color #589A5F;
+@define-color label #C0C396;
+@define-color image #C0C396;
+@define-color progress #C0C396;