Bump version / release notes

[chrisbrahms]

I'll use this PR to collect release notes for Luna v0.7. I'll wait for a few more current PRs to be merged before tagging a new release.

Release notes:

Breaking changes

• The Ionisation module has been refactored to replace closures with functors (callable Structs) (Refactor Ionisation module #410). This simplifies the interface significantly, but the names for several important functions have changed:
  • The closure factories ionrate_fun!_PPTcached, ionrate_fun!_ADK, etc. have been replaced with constructors, IonRatePPTCached, IonRateADK etc. The function signatures are unchanged, so a simple find & replace should suffice (ionrate_fun!* -> IonRate*)
  • The simple functions ionrate_PPT and ionrate_ADK, which calculate the ionisation rate directly, have not changed--they simply create the respective IonRate instead.
• Also as part of Refactor Ionisation module #410 , the ADK ionisation rate now includes an occupancy factor to take into account the spin degree of freedom. This has the same behaviour as for the PPT rate, i.e. it defaults to multiplying the overall rate by 2. This means that simulation results using the ADK ionisation rate may change from Luna v0.6 to v0.7.
• The default noise model used in prop_capillary has changed from the "one-photon-per-mode" noise to noise only being added to the nonlinear response as per arXiv:2410.20567. Re-running previous noise-sensitive simulations with the same RNG or seed will produce different results on Luna v0.7. For more details see New noise model #414.

Other changes

• We fixed the simple interface so that multiple modes are correctly created when requiring both degenerate/rotated modes for the HEnm modes when n is not 1 (enable orthogonal polarisation for HEnm with n != 1 #413)
• Fixed a bug in the scan interface which sometimes caused repeated execution of a scan (thanks to @jtravs, see New noise model #414)