The current @mention (for user names and channel names) uses the regex `\b` to detect the name boundaries, however that token doesn't support unicode characters. This solution replaces the word boundary with regex that match end of the word with any of the following white space, colon, comma and dot.

However, ending a name with a dot still has a problem as it doesn't get a mention link and this fix does not fix it. Part of the problem is that dots are allowed in the name validation regex. So this problem need to be solved later.

Another thing that this fix adds is a description to the UTF8 Name Validation settings, to inform chat admins about the characters that they need to avoid using in their regexes to not break other chat functionalities that depends on special characters to denote special meanings.

Code blocks and inline code that are preceded by RTL text will get displayed in RTL, and that breaks the formatting. This fix forces it to always display in LTR

Currently when you upload an image as an avatar, the "SELECT FILE" button disappears and you get another button to use the uploaded file. However, if you didn't like how the uploaded image looks you cannot upload another one. The work around is to reopen the avatar settings page, instead the upload button should stay there to allow the user to upload a different image.

In RTL interface if the file name  has only number, or included RTL characters the file extension will be shown in the wrong side. This fix makes file extensions show correctly for all files

Removed the trash icon since the buttons are used to upload files and not delete them