Improve the url parsing when using relative URLs

[carbonrobot]

Refactor URL parsing so we can correctly handle relative URLs passed to fetch via the browser. Uses a localhost fallback so we don't crash the application. Improves testing by covering the fetch.ts file to 100%

Fixes #129

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 0eb74429cbb4064e334763f1ef6e92edad4625a8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

| Name | Type | | -------------- | ----- | | @envyjs/core | Patch | | @envyjs/node | Patch | | @envyjs/web | Patch | | @envyjs/webui | Patch | | @envyjs/apollo | Patch | | @envyjs/nextjs | Patch |

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR