Enhancement: Improve validation of arrays inside `.htmlhintrc`

[gian1200]

Description

As explained in #287 (comment), validation of attr-value-no-duplication and attr-lowercase do not include element types inside the arrays.

Suggestion

Reading https://stackoverflow.com/questions/77071094/json-schema-allow-multiple-types-in-array-while-specifying-the-order-and-amount, I think this could be done to solve it:

"attr-lowercase": {
    "description": "Attribute name must be lowercase.",
    "anyOf": [
        { "type": "boolean" },
        { "type": "array", "items": { "type": "string" } }],
    "default": false
},
...
"attr-value-no-duplication": {
    "description": "Class attributes should not contain duplicate values. Other attributes can be checked via configuration.",
    "anyOf": [
        { "type": "boolean" },
        { "type": "array", "items": { "type": "string" } }],
    "default": false
},

Place to change

https://github.com/SchemaStore/schemastore/blob/master/src/schemas/json/htmlhint.json