adding spectra-cpp

[timkpaine]

Checklist

• [x] Title of this PR is meaningful: e.g. "Adding my_nifty_package", not "updated meta.yaml".
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[conda-forge-webservices[bot]]

Hi! This is the friendly automated conda-forge-linting service.

I wanted to let you know that I linted all conda-recipes in your PR (recipes/spectra-cpp) and found some lint.

Here's what I've got...

For recipes/spectra-cpp:

• about/license_family 'MPL' not allowed. Allowed families are AGPL, APACHE, BSD, CC, GPL, GPL2, GPL3, LGPL, MIT, MOZILLA, NONE, OTHER, PROPRIETARY, PSF, and PUBLIC-DOMAIN.

[conda-forge-webservices[bot]]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipes/spectra-cpp) and found it was in an excellent condition.

[timkpaine]

@conda-forge/help-c-cpp all set, header-only library but some tests fail (they also fail for me locally outside of conda), so I've disabled those tests and leave up to the end user to decide if this is a problem.