49876014

Feat/add append instruct to signatures (#9923)

* add append instructions function

* add unit tests

* tweak comments

* Update dspy/signatures/signature.py

Co-authored-by: greptile-apps[bot] <165735046+greptile-apps[bot]@users.noreply.github.com>
Signed-off-by: Karthik Mathur <22126205+mathurk1@users.noreply.github.com>

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Signed-off-by: Karthik Mathur <22126205+mathurk1@users.noreply.github.com>
Co-authored-by: greptile-apps[bot] <165735046+greptile-apps[bot]@users.noreply.github.com>