feat: add `blas/base/igamax`

[aman-095]

Description

What is the purpose of this pull request?

This RFC proposes to add a routine to find the index of the first element having maximum absolute value as defined in BLAS Level 1 routines. Specifically adding @stdlib/blas/base/igamax is proposed.

Related Issues

None.

Questions

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No.

Other

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No.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• [x] Read, understood, and followed the contributing guidelines.

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@stdlib-js/reviewers

[aman-095]

I explored and added the implementation for the generic routine of idamax. Once idamax and isamax are reviewed and merged, this can also be reviewed.

[kgryte]

@aman-095 You'll want to update this PR to handle accessor arrays (see gcopy and gswap), which will include updating the implementation and adding associated tests. In order to handle complex number arrays, we'll need to implement dcabs1 and scabs1 (as in izamax and icamax).

[aman-095]

Sure @kgryte I am currently working on cscal, and after this, I will start working on this as well. 

[kgryte]

Now that we've added dcabs1 and scabs1, I believe this PR is no longer blocked and can be updated per the discussion above.