[TODO] make `task` string msg optional: most ppl just have a useless name
a lot of taks are written as:
```nim
task test, "Test":
  ...
```
or 
```nim
task test, "":
  ...
```

so how about making that string optional, allowing however wants to have a useful string to write it, and others to just use:
```nim
task test:
  ...
```
