Remove unnecessary dependencies

[timmorey]

We've been getting misleading security reports about vulnerabilities in our dependency chain under this package, but it doesn't look like those things actually need to be dependencies. In particular, the npm dependency pulls in a version of semver vulnerable to https://nvd.nist.gov/vuln/detail/CVE-2022-25883.

While I don't believe this package really exposes our users to that vulnerability, I'd rather clean up the package than argue with our security team. This should also marginally improve install speed and reduce bloat where this package is used.

These dependencies were added with #169, and @ungap/structured-clone is a legitimate dependency. The @types package just needs to be listed as a dev dependency to get its goodness. I wasn't actually able to find any indication that the i package is in use, but would be happy to add it back in if there is need.

[timmorey]

I have a hypothesis about how the npm and i deps may have been introduced:

1. Developer has intent to install new packages @ungap/structured-clone and @types/ungap__structured-clone
2. Developer starts typing into the terminal npm i to follow through on their intent
3. Developer gets interrupted or distracted
4. Developer later picks up where they left off and enters npm i @ungap/structured-clone @types/ungap__structured-clone --save into the terminal and hits Enter, forgetting that npm i was already entered. The full command npm i npm i @ungap/structured-clone @types/ungap__structured-clone --save gets executed.

[timmorey]

@snewcomer any chance this could get a review and release? Preferably with a patch version bump only (1.3.5), so this can slide into our transitive dependencies without having to update references in consuming packages.