Now ,icon is visible in the chrome extension dashboard and the tabs

Fixes #46 (closed)

Before changes :

After Changes:

Changes proposed in this pull request:

• added "icons": { "16": "./images/default_icon_16.png", "32": "./images/default_icon_32.png", "48": "./images/default_icon_48.png", "128": "./images/default_icon_128.png" },in the manifest.json

Checklist

• My branch is up-to-date with the Upstream develop branch.
• The acceptance, integration, unit tests and linter pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)