0.2.1 release issues overview

[yucongalicechen]

docs:

• getting started documentation #114
• update doc/tutorial for gooey #132
• GUI widget only supports files, folders must be typed - needs docs clarification #148
• docs: functions module #157
• docs: tools module #158
• docs: labpdfprocapp.py #159

diffpy.utils related:

• Change slope bounds and number of loops in mud_calculator.py #122
• Check updates from diffpy.utils #129
• feat: add load_user_info with options for orcid and skip_creation_config` #150
• fix: refine docstring and test annotation following new group standard #152

muD:

• muD lookup table #9
• Implement multiple options for computing muD #143
• feat: lpp-getmud module that returns best mu or D for given muD #166

other features:

• add gooey support so it can be run with a gui #57
• implement other x-axes #45
• Remove duplicated wavelength from output files #121
• fix: skpackage v0.1.0: modify .github and .pre-commit-config.yaml. Follow new practices for writing commit/issue and news.rst file #149
• fix: update wavelengths #153
• feat: add config workflow for wavelength #160
• feat: workflow for getting wavelength/anode type #161
• feat: muD fast calculation for values <0.5 and >6 #167