Offer completion and syntax highlighting for inlined CSS & HTML in JS/TS/JSX/TSX

The wwd uses a generic editor to open html, css, js, jsx, ts, tsx, etc.

Would be nice to support all these languages (code completion and syntax highlighting) within this generic editor. It should not matter, which language is within which filetype. For example, if wwd detects css or html within js/jsx/ts/tsx files, then it should provide code completion and syntax highlighting. As css and html can be added within js/jsx/ts/tsx files (for example, by template literals), the generic editor should be a hybrid editor.

Please improve at least these cases:

• There is actually no content assist and code highlighting of html and css placed within a template literal in a .js-file. Please provide support.

• There is actually content assist and syntax highlighting of html in jsx, but typing, for example, a <div>- tag does not automatically produce its closing tag. So I have to add it manually.

• Using html and css within template literal should provide content assist and code completion within this generic editor for ALL file types.

For example:

// defined within js file (html and css within template literal -> no code completion/no syntax highlighting)
const component = {
            label: `<span style="color: red">hello</span>`,
            input:`<input name="hi" type="checkbox" ${conf.enabled ? 'checked' : ''} ${!conf.disabled ? 'disabled' : ''}>`,
            isCheckbox: true
    }

There were efforts in the past in this direction https://github.com/eclipse/wildwebdeveloper/issues/151. But the css, html support (=code completion and syntax highlighting) in template literal and within js, jsx, ts, tsx is not sufficient.

Start by reviewing the generic editor behavior described here and the earlier effort in issue 151. Reproduce the listed JavaScript, JSX, TypeScript, TSX, template-literal, HTML, and CSS cases; done means content assist, syntax highlighting, and automatic HTML closing tags work across the requested file types.