Shell Commands

If you face error like raco tr cannot find such command, run raco setup.

Run raco tr build to build HTMLs
Run raco tr watch to watch content changes and build on fly
Run raco tr next to get next available address, for example, you might like to run
```
vi $(raco tr next xxx).scrbl
```
to work on a new file (replace vi with any command line editor command)

The output directory is _build, run python3 -m http.server -d _build to view result, or upload it to host.