Update README.md: Fix Quick Example Config

[carloluis]

Fix Quick Example

Make JSON Configuration valid

What this PR does / why we need it:

Correct the JSON format in the README example so that it can be copied & pasted as a valid initial config. for the plugin.

Vim/README.md

Lines 118 to 123 in 02cf1f3

	"// To improve performance",
	"extensions.experimental.affinity": {
	"vscodevim.vim": 1
	}
	}
	```

Which issue(s) this PR fixes

Special notes for your reviewer:

[J-Fields]

Thanks!