Support for attribute wildcards

This release adds support for the attribute wildcard @* that can be used to extract all HTML attributes from an element:

echo "<a href='#' rel='noopener' target='_blank'>Click me</a>" | hred 'a @*'

[
  {
    "href": "#",
    "rel": "noopener",
    "target": "_blank"
  }
]

v3.2.0

• Prefer the => operator instead of >> for defining aliases. The old operator is kept for backwards compatibility.
• Adds the ... (spread) operator equivalent to the . alias
• Use the .scoped key when using the . alias and not all keys are named.

v3.1.3

Bug fix: parse selectors such as a[href^="#"] correctly.

v3.1.1

Added more comprehensive error handling.

v3.0.3

Added the . special alias.

v3.0.2

New features:

• pick the first matching element for a selector with the ^ prefix;
• alias attributes, properties, and scoped selectors with the >> operator.

v2.0.0

Breaking change: changed attribute selector from $ to @ for easier compatibility with the command line.