Accept the same arguments as dict constructor for template rendering functions

[MattyMay]

The template rendering functions currently only accept named arguments to build the context dictionary passed to jinja2.Template.render(). While unpacking is easy enough, it would be nice to be able to use the same arguments as the dict constructor (like how Jinja's render function works).

Examples:

flask.render_template("index.html", {"greeting": "Hello", "name": "World"})
flask.render_template("index.html", {"greeting": "Hello"}, name="World")

I'll link a PR in case this is something people would like.

[davidism]

Thanks, but I prefer keeping this API simple, as you say dict unpacking already handles this.