T58: the terminal shows a scrollbar over its history, which a user asked for in issue #2 after 0.1.5, since a program that takes the mouse takes the wheel: a thumb along the right edge, in Ely's sizes and colors, stands where the view stands, and a drag moves the view through the history; none shows without history

src/term/mod.rs

@@ -16,6 +16,7 @@ mod pointer;
 mod prompts;
 mod pty;
 mod reports;
+mod scrollbar;
 pub mod shell;
 mod status;
 mod tap;