French localisation & language selection to IMAGE UI

Changes made:

Refactored hardcoded text into locale messages:
- Rendering options
- Advanced options
- Developer Mode
- "Cancel" & "Save Changes" buttons
- Misc. texts: Server, Developer Mode Description
Translated English locale messages to French
Added class="localisation" to be able to obtain a list of text fields from option.ts
Changed IDs of labels for consistency throughtout the locale messages files
Add

Added Language selection field to UI with drop-down box with 3 options: Automatic, English, French
Added async function to get user's language selection from extension
Added warning messages indicating limitation to non-English rendering options.

Made cursor become a pointer when hover through "Cancel" or "Save Changes" buttons.
Minor formatting in options.html for visual and consistency.

In order for "Automatic" Language selection mode to work, browser's locale must be set to user's desire language. Follow guide here chrome.i18n How to set browser's locale
- (Linux) E.g. I use Vivaldi browser on Arch Linux. To change browser's locale, I must change the $LANGUAGE environment variable. Because I never set it in /etc/environment, I must do: (different Linux distros may have different solution)
```
$ export LANGUAGE="fr" # only works for 1 terminal session
$ vivaldi-stable
```
The extension in Automatic Language mode will follow the browser's locale language, "en" xor "fr". Test on any graphic and verify.