Always use style color for plain text

Before this change, it only worked on 16M color terminals.

After there's a Chroma release with
alecthomas/chroma#869 in it we should revert
back to "None" here and use the new Chroma release instead.

m/pager.go

@@ -450,7 +450,12 @@ func (p *Pager) initStyle() {
 
 	stringBuilder := strings.Builder{}
 	err := (*p.ChromaFormatter).Format(&stringBuilder, p.ChromaStyle, chroma.Literator(chroma.Token{
-		Type:  chroma.None,
+		// FIXME: They Type here should really be None. "Background" is a
+		// workaround until we can bump Chroma to a release with this change in
+		// it:
+		// https://github.com/alecthomas/chroma/pull/869
+		Type: chroma.Background,
+
 		Value: "XXX",
 	}))
 	if err != nil {