feat: implement phase 4 batch — 54 base-class wrapper sources

Add 8 all/ sources (7 Masonry, 1 Madara) and 38 en/ sources spanning
Madara, MangaThemesia, MadTheme, Keyoapp, and Guya bases, plus 8 earlier
all/ standalone sources from the previous session (ahottie, akuma,
allporncomicsco, asmhentai, baobua, beauty3600000, buondua, comicfury,
comicgrowl, comicklive, comicsvalley, comikey, commitstrip, coomer).

Also annotates phase4-standalone.md with base-class tags for 43 additional
unimplemented en/ sources identified in a full scan.

sources/en/mangagg/mangagg.go

@@ -0,0 +1,16 @@
+package mangagg
+
+import (
+	"goyomi/internal/registry"
+	base "goyomi/sources/base/madara"
+)
+
+func New() *base.Source {
+	return base.New(base.Config{
+		Name:    "MangaGG",
+		BaseURL: "https://mangagg.com",
+		Lang:    "en",
+	})
+}
+
+func init() { registry.Register(New()) }