Explicitly list files to be included in package

[LinusU]

I noticed that some of my VSCode configs were being published along with the module 😂

This PR changes to an explicit list to things to include, instead of an ignore-file.

This is the difference in published files:

--- a	2019-01-14 18:31:52.000000000 +0000
+++ b	2019-01-14 18:32:04.000000000 +0000
@@ -1,15 +1,9 @@
 package.json
-.travis.yml
-appveyor.yml
 binding.gyp
 browser.js
 CHANGELOG.md
 index.js
 Readme.md
-.github/ISSUE_TEMPLATE.md
-.github/PULL_REQUEST_TEMPLATE.md
-.vscode/c_cpp_properties.json
-.vscode/settings.json
 lib/bindings.js
 lib/canvas.js
 lib/context2d.js

ping @zbjornson, @chearon do you think it's a good approach? ☺️

[zbjornson]

👍 for some reason I was just looking at this this weekend!

[chearon]

Sure, does this mean we could/should get rid of npmignore?

[LinusU]

[...] get rid of npmignore?

yeah, it's removed in this PR ☺️