Level_name options

[funtus00]

It would be great to have optional level_name name. For example NLog has feature to make level_name as 1, 3 letters or full name. Current situation (log strings):

[2022-21-12 10:10:01.718][INFO][127.0.0.1] '6': user login [2022-21-12 10:10:01.724][WARNING][127.0.0.1] '6': domain gmail.com is forbidden to use or does not exist
[2022-21-12 10:10:01.724][ERROR][127.0.0.1] '6': user email is forbidden to use

If set it level_name as 1 or 3 letters logs can be like this:

[2022-21-12 10:10:01.718][INF][127.0.0.1] '6': user login [2022-21-12 10:10:01.724][WRN][127.0.0.1] '6': domain gmail.com is forbidden to use or does not exist
[2022-21-12 10:10:01.724][ERR][127.0.0.1] '6': user email is forbidden to use

[2022-21-12 10:10:01.718][I][127.0.0.1] '6': user login [2022-21-12 10:10:01.724][W][127.0.0.1] '6': domain gmail.com is forbidden to use or does not exist
[2022-21-12 10:10:01.724][E][127.0.0.1] '6': user email is forbidden to use

It helps to read logs. Idea do make option: INFO = INF = I ERROR = ERR = E WARNING = WRN = W DEBUG = DBG = D and so on...

[Seldaek]

So this would be for LineFormatter only right? Probably could easily be added as an additional option via a setMaxLevelNameLength(1)? Would you like to send a PR?