build: switch from yarn to npm to manage js dependencies and move js contents to root

yarn v1 is being deprecated and starts to have some issues

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

tests/unit/.eslintrc.js

@@ -0,0 +1,9 @@
+module.exports = {
+  env: {
+    mocha: true,
+  },
+  globals: {
+    expect: true,
+    sinon: true,
+  },
+};