Adds timestamps to the log format

[SirMoM]

Add timestamps to be used in the log format.
And updates the README.md to reflect the changes and give more insight to the formatting options.

Example:

var msg: String = "Error occurred!"

Logger.get_module("main").time_template = "dd.mm.yyyy hh:MM:ss"
Logger.error(msg)

Logger.get_module("main").time_template = "hh:MM:ss"
Logger.error(msg)

Logger.output_format = "[{LVL}] {MSG} at {TIME}"
Logger.error(msg)

Results in:

I mentioned a timestamp system in #9

[SirMoM]

Is there any problem with the pull request?
Or are you just busy @akien-mga ?
I don't want to be annoying but I'm a bit confused why this PR is halted 😬

[akien-mga]

Is it really necessary to make this a per-module configuration, instead of having it global like output_format? To me both output_format and this new time_template serve a similar purpose, I'm not sure why you would want to have a single output format with different timestamp formats based on the module.

I also have style changes to make to the added documentation, I'll push them directly as a commit to this PR once we agree on making this global or module-specific.

[akien-mga]

Here's my proposal to simplify the API and improve the docs and formatting: akien-mga@3dfd241

If you're OK with the changes I'll squash the two commits and push to update this PR and merge.

[akien-mga]

Also, did you follow any specific standard for the timestamp placeholders?

Going by https://en.wikipedia.org/wiki/ISO_8601 (which seems to match Unix timestamp), these would be better:

YYYY
MM
DD

hh
mm
ss

[akien-mga]

New commit: https://github.com/akien-mga/godot-logger/tree/SirMom-feature/log-timestamp

Edit: Updated after actually testing my changes and finding some issues.

[SirMoM]

Is it really necessary to make this a per-module configuration, instead of having it global like output_format? To me both output_format and this new time_template serve a similar purpose, I'm not sure why you would want to have a single output format with different timestamp formats based on the module.

I also have style changes to make to the added documentation, I'll push them directly as a commit to this PR once we agree on making this global or module-specific.

I did that because I thought the purpose of the modules is the configuration of the log message and thus I put in the Module.
But if we ditch the modules altogether then this is fine, but this is up for discussion in #13.

[SirMoM]

Also, did you follow any specific standard for the timestamp placeholders?

Going by https://en.wikipedia.org/wiki/ISO_8601 (which seems to match Unix timestamp), these would be better:

YYYY
MM
DD

hh
mm
ss

No I did not follow any standard but had this in mind. Yes following this is a way better approach!

[akien-mga]

I did that because I thought the purpose of the modules is the configuration of the log message and thus I put in the Module.

Modules are not specifically for configuration, but to have different channels for different types of log messages. E.g. in a networked game you could have a "Server" module and a "Client" module, etc.

I'm not against making configuration module-specific, but that adds configuration overhead every time you create new modules (and this would require making output_format a module specific option too, otherwise it doesn't make much sense to configure e.g. the timestamp format here if you can't configure the output format on a module level).

[akien-mga]

Thanks!