Vscode-spell-checker: Update README instructions

[AlekSi]

I generated Go words for Go 1.9: https://github.com/AlekSi/go-words/blob/master/go.txt

I wanted to contribute them but looks like README is outdated. It says:

The source text for each dictionary is in ./server/dictionaries.

But this directory does not exist.

Use the npm run build-dictionaries command to build the dictionaries for the extension.

But this script does not exist.

[AlekSi]

Ok, I found it – in the other repository in another account. 😕

[Jason3S]

Thank you. The documentation is out of date.

I have been slowly moving all the dictionaries to cspell-dicts. The idea is to make it easy to add more dictionaries and extension add ons.