Feat: report request and error to rollbar

[jmfederico]

Rollbar knows how to report extra request data and extract information from errors if it is explicitly told to do so.

This PR takes inspiration from the official rollbar-go client and its Log function to do so.

Change sin this PR:

• Implement a default ReplaceAttr to remove *http.Request attributes (as rollbar breaks if they are passed to it)
• Extract *http.Request and error objects from slog.Record
• Dispatch the correct reporter method following the same logic as the official rollbar-go client

[jmfederico]

Closing in favour of #2.
New branch name needed since go would not allow having "/" in version specifier for replace directive in go.mod

This is valid:
replace github.com/samber/slog-rollbar/v2 v2.6.0 => github.com/jmfederico/slog-rollbar/v2 report-request-and-error

This is not
replace github.com/samber/slog-rollbar/v2 v2.6.0 => github.com/jmfederico/slog-rollbar/v2 feat/report-request-and-error

[samber]

i was reviewing it anyway ;)