Editorial: update to modern Web IDL conventions (#1528)
* Editorial: update to modern Web IDL conventions
* Uses "getter steps" and "method steps"
* Use "this" instead of "context object"
* Talk about dictionaries as Infra maps
* Minor restructuring of promise-creation/in parallel algorithms for NavigationPreloadManager
* Update docs/index.bs
* Update docs/index.bs
* Update docs/index.bs
* Update docs/index.bs
* Update docs/index.bs
* Update docs/index.bs
* Update docs/index.bs
* Update docs/index.bs
Co-authored-by: Jake Archibald <jaffathecake@gmail.com>
