Function normalize_root

pub fn normalize_root(v: &str) -> String

Make sure root is normalized to style like /abc/def/.

Normalize Rules

• All whitespace will be trimmed: abc/def => abc/def
• All leading / will be trimmed: ///abc => abc
• Internal // will be replaced by /: abc///def => abc/def
• Empty path will be /: `` => /
• Add leading / if not starts with: abc/ => /abc/
• Add trailing / if not ends with: /abc => /abc/

Finally, we will get path like /path/to/root/.