chore: adding plugin-fetch and example (open-telemetry#1121)

* chore: adding plugin-fetch and example

* chore: investigating failing test

* chore: chore fixing tests with better fetch mocking

* chore: addressing comments

* chore: lint

* chore: addressing comments

* chore: updating webpack-env

* chore: fixes after update for node types

* chore: addressing reviews

* chore: fixes after merge

* chore: updating version

Co-authored-by: Mayur Kale <mayurkale@google.com>
Co-authored-by: Daniel Dyla <dyladan@users.noreply.github.com>

api/karma.base.js

@@ -20,7 +20,7 @@ module.exports = {
   browsers: ['ChromeHeadless'],
   frameworks: ['mocha'],
   coverageIstanbulReporter: {
-    reports: ['json'],
+    reports: ['html', 'json'],
     dir: '.nyc_output',
     fixWebpackSourcePaths: true
   },