added todo.md, submitted by ~ensa

pages/todo.md

@@ -0,0 +1,66 @@
+<!--
+title: todo, a todo list manager
+description: todo usage guide
+author: ensa
+-->
+
+# todo, a todo list manager
+
+`todo` is a todo list manager.
+
+`todo` manages the todo list stored in the path referred to by `$TODO`, or
+`$HOME/todo` if TODO isn't set.
+
+## basic usage
+
+`todo` without arguments will print the file's
+contents, with line numbers added.
+example output:
+```
+     1  write todo documentation
+     2  water the cat
+     3  do nothing
+```
+
+`todo -a "MSG"`
+will append another line, containing MSG.
+```
+     1  write todo documentation
+     2  water the cat
+     3  do nothing
+     4  MSG
+```
+
+`todo -e` edits the todo file in `$EDITOR`.
+
+`todo -d 2` removes item 2 from the list, and archives it in `${TODO}.complete`
+with a timestamp.
+`todo` output after `todo -d 2`:
+```
+     1  write todo documentation
+     2  do nothing
+     3  MSG
+```
+
+`todo -x` views the list archive.
+example output:
+```
+2020-07-16 13:37:53 - water the cat
+```
+
+## advanced use
+
+the `-n` flag specifies the line number where the line is added, pushing all
+lower lines down by one.
+for example, `todo` after `todo -n 3 -a 'bake pie'` will result in this.
+```
+     1  write todo documentation
+     2  do nothing
+     3  bake pie
+     4  MSG
+```
+
+## source repository
+todo's source can be found [here](https://git.tilde.institute/ensa/todo).
+
+[back](/)