Pyfstat

- PyPI source tarball for v1.11.4 didn't include files needed to build conda package
- improved codecov setup
- no actual changes to package

- python 3.9 now supported
- improvements to documentation and examples
- for developers: flake8-docstrings and flake8-executable rules now enforced
- added a codemeta.json file
- started tracking test coverage with codecov

- added LineWriter class for simulating unmodulated noise artifacts

- pinned numpy dependency to <1.20 to fix incompatibility with lalsuite 6.81
- updated ephemerides instructions and citation requests in README
- fixed FrequencyModulatedArtifactWriter class

- matplotlib will no longer be automatically forced to `agg`,
but only if `env["DISPLAY"]` is not set
- improved default scaling of MCMC corner plots
- fixed missing unit for `tp` binary parameter in MCMC default plot labels

- LALSuite >= 6.80 now required
- simplified calls to F-stat prediction
- Writer:
- internal cleanup of sftfilenames vs sftfilepath
- SFTs are validated at end of `run_makefakedata()`
- core and search classes: improved and fixed non-standard detection statistics
- fixed basic twoFX and BSGL computation logic for transient and semicoherent cases, generalized to Ndet>2
- reorganised methods for these computations
- additional results are stored as class attributes
- for transients, the detection statistic is now called explicitly `maxTwoF`
- grid classes now initiate their `.search` object at instantiation instead of at first `run()` call