readme TODOs updated

README.md

@@ -14,15 +14,25 @@ A command line application and Python library for generating binary numbers for
 ```make_binary_problems <number_of_bits: integer> <number_of_problems: integer>```
 
 ## TODO
-- add nice spacing for easy reading
+- add nice spacing and typography for easy reading
 - pdf options
   - problem numbers [true]
   - number of columns [auto]
   - font
   - include column labels
   - print
+- addition
+- subtraction
+- mult? div?
+- hex?
 
 ### Other Projects That Could Depend On This
 - do the problems online/on computer
 - a website to serve these up and let people use them for free
   - a web API that serves it, so people can do that programmatically
+  - a snail mail service?
+    - https://developers.lulu.com/price-calculator
+  - if there's going to be exercises in the browser,
+    - parseInt('0101', 2)
+  - maybe re-implement in Javascript so all computation and rendering is done on the client
+    - [PDF rendering in the browser](https://pspdfkit.com/blog/2018/render-pdfs-in-the-browser-with-pdf-js/)