Adds .html.erb to erb language extensions for toggleTags command

[kjleitz]

Previously the ctrl+shift+` keybinding did not work out-of-the-box in *.html.erb files (the default extension for erb views in Rails). This PR adds that file extension to the erb language definition in package.json.

This may have been the source of https://github.com/vortizhe/vscode-ruby-erb/issues/5

[seanharmer]

Any chance of getting this merged please?

[jonathansimmons]

@vortizhe This really is a necessity for this extension. Please merge.

[kirillplatonov]

Fixed in my fork: https://marketplace.visualstudio.com/items?itemName=kirillplatonov.erb-toggle