Add unit specifier support for UTC offset and timestamp parsing in decoder options

[coderabbitai]

Feature Request

Add support for unit specifiers in decoder options to allow developers to specify the units for UTC offset and timestamp fields when parsing IR files.

Context

Currently, the decoder assumes specific units for time-related fields:

• UTC offsets may be stored in seconds but JS libraries typically expect minutes
• Timestamps have similar unit assumption challenges

Proposed Solution

Add unit specifier options to the decoder configuration, such as:

• unit="h"/"m"/"s" for hour/minute/second units
• unitInMillis=3,600,000/60,000/1,000 for specifying units in milliseconds

This should apply to both:

• UTC offset parsing
• Timestamp parsing

References

• Original discussion: feat: Add support for parsing UTC offset in seconds per log event and returning it in decode results (resolves #79). #99 (comment)
• Related to PR: feat: Add support for parsing UTC offset in seconds per log event and returning it in decode results (resolves #79). #99

Requested by: @hoophalab