Voice Fill icon is wrongly displayed on Google RTL pages

[SoftVision-CosminMuntean]

[Affected versions]:

• Firefox 55.0.3 and up
• Voice Fill 1.3.0

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Latest Voice Fill add-on (1.3.0) was previously installed on a clean profile.
• Tools -> Page Info -> Permissions -> Use the Microphone -> "Use Default" is unchecked and "Block" is checked.

[Steps to reproduce]:

1. Open the browser with the profile from prerequisites and navigate to "https://www.google.ae/" page.
2. Perform a search on Google page.
3. Observe the Voice Fill icon position.

[Expected result]:

• The Voice Fill icon is displayed on the left part of the Search bar.

[Actual result]:

• The Voice Fill icon is displayed on the right part of the Search bar over the "Google" icon.

[Notes]:

• Here is a screen shot with the issue: