`staticDir` extension support ⚡
Well old `staticDir` syntax was:
```nim
# directory is route and directory
staticDir "directory"

# directory at route /path
staticDir "/path" -> "directory"
```

New syntax add file extension support:
```nim
# Path -> directory
staticDir "/public" -> "testdir"

# path -> directory ~ extensions
# On this path user can see only HTML, JS and CSS files
staticDir "/pubdir" -> "testdir" ~ "html,js,css"

# Path and directory ~ extensions
staticDir "/templates" ~ "html,js,css"
```