[Bug] Fails if object has key of ''

[tmeasday]

Describe the bug

These lines:

telejson/src/index.ts

Lines 149 to 150 in 6d2e7a4

	// very first iteration
	if (key === '') {

assume objects cannot have keys ''. As we saw in storybookjs/storybook#20755, that isn't a good assumption.

Steps to reproduce the behavior

## in node REPL

> const b = {}
undefined

> b[''] = { b: b}
<ref *1> { b: { '': [Circular *1] } }

> require('telejson').stringify(b)
Uncaught TypeError: Converting circular structure to JSON
    --> starting at object with constructor 'Object'
    |     <anonymous> -> object with constructor 'Object'
    --- property 'b' closes the circle
    at JSON.stringify (<anonymous>)
    at Object.stringify (/Users/tom/GitHub/chromaui/chromatic/node_modules/telejson/dist/cjs/index.js:467:15)

Expected behavior

It should stringify correctly.