Break current worker attribute dance

[WebReflection]

In a quest to make scripts never ambiguous in their intent, we are going to offer these 4 variants for scripts:

<script type="py">print(1)</script>
<script type="py" worker>print(1)</script>
<script type="py" src="./file.py"></script>
<script type="py" src="./file.py" worker></script>

Breaking

• the worker="..." case will throw a SyntaxError
• the worker empty attribute will bailout ASAP without bootstrapping the interpreter on main