Adjust features list

Author: rocky

README.rst

@@ -14,9 +14,9 @@ Features
    - saving command history between sessions.
    - variable completion, even for symbol names like `\\[Sigma]`
    - limited ESC keyboard input; for example *esc* ``p`` *esc* is π
-* Syntax highlighting using `pygments`.
-* Automatic detection of light or dark terminal background color.
-
+* Syntax highlighting using `pygments <https://pygments.org>`_.
+* Automatic detection of light or dark `terminal background color <https://pypi.org/project/term-background/>`_.
+* Entering and displaying Unicode symbols such as used for Pi or Rule arrows
 
 Installing
 ----------