Updated contents to the regex article

[Kalyan-Lama]

Updated this article with the following:

• Restricting an entry to 10, 13, or 17-digit numbers only (new content)
• Restricting an entry with accent characters (new content)
• Restricting time inputs (new content)
• Restricting a valid email id (update content)
• Restricting all texts to uppercase (new content)
• Restricting all texts to lowercase (new content)
• Restricting the first letter in uppercase (new content)

[Kalyan-Lama]

@joshuaberetta, would you mind reviewing and merging this updated article with the master branch?