Use shorter syntax in README example

[amomchilov]

Just from a quick glance at the README, it's not obvious that there's a shorter single-line syntax that could be used instead of the multiple # @rbs name: Type lines.

When I showed this repo to several coworkers, they all got the mistaken impression that the signitures have to be multiple lines like JavaDoc or JSDoc.

To fix this, I suggest we highlight the short syntax in the first and main example.

Optionally, we could add another method as an example of the longer syntax, showing how it can be useful for methods with many parameters and/or long types, like this one:

rbs-inline/sig/generated/rbs/inline/ast/members.rbs

Lines 109 to 113 in 5b4885b

	# @rbs node: Prism::CallNode
	# @rbs comments: AnnotationParser::ParsingResult?
	# @rbs application: Annotations::Application?
	# @rbs return: void
	def initialize: (Prism::CallNode node, AnnotationParser::ParsingResult? comments, Annotations::Application? application) -> void