Add chart descriptions

Author: kgryte

lib/node_modules/@stdlib/plot/sparklines/unicode/docs/repl.txt

@@ -4,11 +4,11 @@
 
     The following chart types are supported:
 
-    - column
-    - line
-    - tristate
-    - up-down
-    - win-loss
+    - column: column chart (e.g., ▃▆▂▄▁▅▅).
+    - line: line chart (e.g., ⡈⠑⠢⠔⠒⠒⠒).
+    - tristate: tristate chart (e.g., ▄▀──▀▄▄▀).
+    - up-down: up/down chart (e.g., ↓↑↑↑↑↓↓↑).
+    - win-loss: win/loss chart (e.g., ┌╵└┴╵╷╷╵).
 
     The `data` argument takes precedence over the `data` option.