Change parameter type from `String` to `&str` (string slice)

[gauravgahlot]

The new function on many types accepts String parameters. It would be better to change from String to &str (string slice).

Here are a few examples:

• argoflows/src/types/workflow/parameter.rs

  Line 43 in bfd710e

  pub fn new(name: String) -> Parameter {

• argoflows/src/types/template/script_template.rs

  Line 153 in bfd710e

  pub fn new(image: String, source: String) -> ScriptTemplate {