fix(sdk): set the hideNavigation param correctly for embeds

[fvsch]

We have a bug with the hideNavigation option for embed methods.

Instead of adding hideNavigation=1 to the URL, we add hideNavigation=1;, resulting in a value of 1; which gets ignored by the StackBlitz editor.

This PR fixes this issue, and constructs the query string by joining an array of key=value strings instead of adding having to deal with adding & or not for each parameter.

There are a couple other changes:

1. The theme parameter is restricted to 'light' or 'dark'. Though maybe we should accept any string, even though we're not supporting other values? Happy to roll back that change if we want to keep it open. (I’m noticing that it's not documented on https://developer.stackblitz.com/docs/platform/javascript-sdk/#embed-options yet?)

2. The devtoolsheight option now accepts the values 0 and 100. In particular, I’ve seen users of the SDK use devToolsHeight: 99 because 100 was filtered out by the SDK, even though devtoolsheight=100 in the URL does work.