Add environment as a new filter to _cascade.target

Fixes #9612

resources/page/page_matcher.go

@@ -37,6 +37,9 @@ type PageMatcher struct {
 
 	// A Glob pattern matching the Page's language, e.g. "{en,sv}".
 	Lang string
+
+	// A Glob pattern matching the Page's Environment, e.g. "{production,development}".
+	Environment string
 }
 
 // Matches returns whether p matches this matcher.
@@ -67,6 +70,13 @@ func (m PageMatcher) Matches(p Page) bool {
 		}
 	}
 
+	if m.Environment != "" {
+		g, err := glob.GetGlob(m.Environment)
+		if err == nil && !g.Match(p.Site().Hugo().Environment) {
+			return false
+		}
+	}
+
 	return true
 }