Support auto indentation when hitting enter inside a tag

[fbricon]

Similar to the html support in vscode, hitting enter in a xml tag should automatically indent the content.

No idea how it's implemented in the html extension. It's probably a client-side feature, but not necessarily.

[fbricon]

Found the idea in https://stackoverflow.com/questions/51235400/visual-studio-code-auto-close-tag-and-indent-xml-as-with-html

[fbricon]

In the html extension, this is achieved via those dreadful regexp patterns:

languages.setLanguageConfiguration('html', {
    indentationRules: {
        increaseIndentPattern: /<(?!\?|(?:area|base|br|col|frame|hr|html|img|input|link|meta|param)\b|[^>]*\/>)([-_\.A-Za-z0-9]+)(?=\s|>)\b[^>]*>(?!.*<\/\1>)|<!--(?!.*-->)|\{[^}"']*$/,
        decreaseIndentPattern: /^\s*(<\/(?!html)[-_\.A-Za-z0-9]+\b[^>]*>|-->|\})/
    },
    wordPattern: /(-?\d*\.\d\w*)|([^\`\~\!\@\$\^\&\*\(\)\=\+\[\{\]\}\\\|\;\:\'\"\,\.\<\>\/\s]+)/g,
    onEnterRules: [
        {
            beforeText: new RegExp(`<(?!(?:${EMPTY_ELEMENTS.join('|')}))([_:\\w][_:\\w-.\\d]*)([^/>]*(?!/)>)[^<]*$`, 'i'),
            afterText: /^<\/([_:\w][_:\w-.\d]*)\s*>/i,
            action: { indentAction: IndentAction.IndentOutdent }
        },
        {
            beforeText: new RegExp(`<(?!(?:${EMPTY_ELEMENTS.join('|')}))(\\w[\\w\\d]*)([^/>]*(?!/)>)[^<]*$`, 'i'),
            action: { indentAction: IndentAction.Indent }
        }
    ],
});

/me needs to throw up

[fbricon]

Got a fix. Will PR after I get some shut eye.

[fbricon]

Tadaaaa