Display wide characters correctly.

- Made termstr's length match the on-screen width.
  - Achieved by adding a zero width character after each wide
    character.
  - This fixes ljust and rjust, so that there is correct padding,
    otherwise Portal appearances aren't the correct width.
- When getting a sub-string containing half a wide character,
  the half character is a space.
- Some wide characters are still broken. e.g. country flags

install-dependencies

@@ -10,7 +10,7 @@ if [ $DIST_ID != "ubuntu" ]; then
     exit 1
 fi
 echo "Installing the dependencies of the eris script…"
-sudo apt --yes install python3-pip python3.9 util-linux
+sudo apt --yes install python3-pip python3.9 util-linux python3-cwcwidth
 python3.9 -m pip install pyinotify pygments docopt pillow toml
 echo
 echo "Installing all the tools eris may need…"