erblint executable is deprecated in favour of erb_lint

[alessandro-fazzi]

Following this PR Shopify/erb_lint#360 the erblint executable has been deprecated.

As a consequence the plugin is constantly (on each run) re-throwing the deprecation warning within a VSCode's toast.

I noticed that the executable name is hardcoded in

vscode-erb-linter/src/configuration.ts

Line 18 in a2b4127

const cmd = 'erblint'

I don't know how you'd like to handle the transition or the support for older gem versions, but I think support for the correct executable urges.