Speedreader article date should be localized

[rillian]

Description

When speedreader can extract a timestamp from an article, it adds it to the header in the reader-mode version, but it uses a hard-coded US-style format like 'Jan. 01, 2018 12:53 PM' It would be better to present the 'Updated ' text translated and formatted according the the user's locale.

Steps to Reproduce

1. Enable Speedreader
2. Visit a news article
3. Compare date format to locale and time zone

Actual result:

Updated Sep. 05, 2019 17:36 pm

Expected result:

5 November 2019, 11:36
(or some other appropriate local format)

Reproduces how often:

Brave version (brave://version info)

Version/Channel Information:

• Can you reproduce this issue with the current release?
• Can you reproduce this issue with the beta channel?
• Can you reproduce this issue with the nightly channel?

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information: