[Docs]: Correct README.md to match initialize declaration with string argument

[PrajwalHM-Gaargesh]

Modified the initialize function declaration to accept a string parameter in README.md as per the signature of that function in section 2 of Quick start.

[nircoe]

Great catch @PrajwalHM-Gaargesh!
I added the defaultSource argument later on and forgot to update the README!
I think you should mention in the comments where you changed that in this way (passing std::string{}) you will initialize logcoe without an default source.
It's a minor addition, but may be helpful to other users in the future.
Maybe even we should give two examples, one with a defaultSource ("logcoe" for example, so by default the logs we will printing be [timestamp] [log_level] [logcoe]: <log_message>),
and one without - [timestamp] [log_level]: <log_message>, of course it is possible to pass a source when logging, but there will be no default one.
Thanks for your contribution!

[nircoe]

H, Thanks for your updates.
I checked the documentations, you covered all of the appearances of logcoe::initialize() method.
Please just commit a fix to my review (minor changes, formatting issues only).
Afterwards I'll approve the PR, run the github workflows and you will be able to squash and merge.
Please make sure the squashed commit message is the PR title, and mention your changes shortly in the squashed commit message body.
Thanks again!