Update German & Russian localization

• Update German localization (@xyrolaith)
• Update Russian localization (@turisap)
• Add translators section to README
• Update contributing guidelines
• Update donations section in README

Fix resetting options

• Add message handler to set all options to default
• Update options form resetting to set all options to default
• After form reset, update form values from storage

Enable localization of options/preferences page

• Add markup to options form
• Add JavaScript handlers for data-locale-* attributes
• Update English locale as example
• Update README with PayPal donation link

Add support for Feedly

• Add support for Feedly
• Add green RSS icon and set as icon option
• Add options to pick feed service
• Add dedicated function to open feeds
• Add message handler to use openFeed to open feeds
• Pass params via message to background.js to open feeds
• Add ability to convert URL to Feedly format
• Update storage on update to set default feed service (RSS)

Handle disabled state

Handle upcoming issue with visibility in 58
In Firefox 58, pageAction.hide will disable button instead of
hide it. Since, at least for now (or then), this will cause
confusion, implement the following:

• Add new messages for "Unavailable"
• Set title using this message
• Add new icon with opacity of 0.3 for disabled state
• Use these for title & icon by default when scanning
• Update title and icon if feed found

Temporarily disable animations

• Remove animation class from <template>s
• Add CSS linting
• Do not include Rollup.js config file when building add-on

Switch to using synced storage

• Switch to using using browser.storage.sync instead of browser.storage.local
• Add preferences migration script

More customizable

• Allow setting color and font size & family
• Allow selecting template to use
• Allow setting background color & image
• Allow setting padding & margins
• Set styles using CSS custom properties
• Update default options
• Add update script
• Organize resources

Provide install / update script with default options

• Implement install/update script
• Create function to apply options changes based on previous version(s)
• Set icons by object keys instead of paths to avoid invalid paths
• Set default options on first installation
• Remove outdated form labels / notes for options

Fix incorrect icons

• Update values for options form
• Update defaultIcon
• Fixes #41