Ability to customize the profile

[WesCossick]

Right now, the profile is hardcoded as css3, but the W3C CSS Validator supports many options. An incomplete list of valid values is documented here, but there are more available in the dropdown (e.g., css3svg):

<select id="profile_uri" name="profile">
        <option value="none">No special profile</option>
        <option value="css1">CSS level 1</option>
        <option value="css2">CSS level 2</option>
        <option value="css21">CSS level 2.1</option>
        <option value="css3">CSS level 3</option>
        <option value="css3svg">CSS Level 3 + SVG</option>
        <option value="svg">SVG</option>
        <option value="svgbasic">SVG Basic</option>
        <option value="svgtiny">SVG tiny</option>  
        <option value="mobile">Mobile</option>
        <option value="atsc-tv">ATSC TV profile</option>
        <option value="tv">TV profile</option>
</select>

It would be handy if we allowed users to customize this profile via the options for validateText() and validateURL(), similar to the medium setting. Effectively, this would look like:

const result = await cssValidator.validateURL(cssSourceURL, {
    profile: 'css2',
});

Here's where the profile is hardcoded now:

• w3c-css-validator/src/retrieve-validation/build-form-data.ts

  Line 13 in d7cef11

  `Content-Disposition: form-data; name="profile"${CRLF}${CRLF}css3${CRLF}`,

• w3c-css-validator/src/retrieve-validation/build-request-url-parameters.ts

  Line 12 in d7cef11

  profile: 'css3',

The default value, if none is specified, should remain css3.