Allow custom reset for after function

[brianignacio5]

Description

This pull request adds support for a new "custom_reset" mode to the ESPLoader's reset functionality. It introduces a new reset mode type, updates the after method to accept a custom sequence string, and implements logic to handle custom reset sequences.

Custom reset mode support:

• Added "custom_reset" to the After type definition in src/types/resetModes.ts, allowing it to be used as a valid reset mode.
• Updated the after method in ESPLoader (src/esploader.ts) to accept an optional sequenceString parameter for specifying the custom reset sequence.
• Implemented logic in the after method to handle "custom_reset": it checks for the presence of a sequence string and a custom reset constructor, logs appropriate messages, and executes the custom reset if both are provided.

Fixes #210

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Checklist

Before submitting a Pull Request, please ensure the following:

• 🚨 This PR does not introduce breaking changes.
• All CI checks (GH Actions) pass.
• Documentation is updated as needed.
• Tests are updated or added as necessary.
• Code is well-commented, especially in complex areas.
• Git history is clean — commits are squashed to the minimum necessary.

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Download the artifacts for this pull request:

• esptool-js-0.5.7.tgz.zip