Allow Colon : in HTML Attribute Names

[marcoroth]

This pull request updates the parser to allow HTML Attributes to start with a colon, which is typical in the Vue.js style:

<div :class="classes"></div>

Previously, this caused a syntax error:

@ UnexpectedError (location: (1:5)-(1:6))
├── message: "Unexpected Token. Expected: `TOKEN_IDENTIFIER, TOKEN_AT, TOKEN_ERB_START,TOKEN_WHITESPACE, or TOKEN_NEWLINE`, found: `TOKEN_COLON`."
├── description: "Unexpected Token"
├── expected: "TOKEN_IDENTIFIER, TOKEN_AT, TOKEN_ERB_START,TOKEN_WHITESPACE, or TOKEN_NEWLINE"
└── found: "TOKEN_COLON"

Now this parses as:

@ HTMLAttributeNode (location: (1:5)-(1:21))
├── errors: []
├── name: 
│   └── @ HTMLAttributeNameNode (location: (1:5)-(1:11))
│       ├── errors: []
│       └── children: (1 item)
│           └── @ LiteralNode (location: (1:5)-(1:11))
│               ├── errors: []
│               └── content: ":class"
│                      
├── equals: "=" (location: (1:11)-(1:12))
└── value: 
    └── @ HTMLAttributeValueNode (location: (1:12)-(1:21))
        ├── errors: []
        ├── open_quote: """ (location: (1:12)-(1:13))
        ├── children: (1 item)
        │   └── @ LiteralNode (location: (1:13)-(1:20))
        │       ├── errors: []
        │       └── content: "classes"
        │       
        │   
        ├── close_quote: """ (location: (1:20)-(1:21))
        └── quoted: true

[tvdeyen]

OMG Thanks! 🙏🏻