Structured Headers Hard Mode per Mike Taylor

The goal is to identify servers that are not able to handle Structured Header syntax (and ideally let them know).

Note: this add-on may break things! If something does not work, click on the icon to disable it globally. Clicking again will re-enable it. Feel free to file issues at https://github.com/miketaylr/structured-headers-hardmode if you identify a broken site or service after installing this addon.

These are the 2 headers and their values that are injected:

```
sec-hardmode-list: "b", c1/2, "good"\\luck", ("foo"; a=1;b=?0);lvl=5, (), (e f);lvl=-1
sec-hardmode-dict: lol="ok", sup=:w4ZibGV0w6ZydGU=:, a=(1 2.1), c=4;aa=bb, d=(5 6);cool
```