Put the troubleshooting section back in the README

[tatsuya6502]

• Put the troubleshooting section back in the README, with some rewritten content:
  • When I released v0.12.10, I removed the troubleshooting section because the problems listed in that section should not occur in v0.12.10 or later.
  • However, I realized that users with older versions may still see the README in this repository, so it is worth keeping the section.
• Remove the FOSSA badge from the README.
  • The FOSSA license scan no longer works for some reason.
• Update the copyright year in the LICENSE files.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.25%. Comparing base (e05781b) to head (41cecc5).
Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #486   +/-   ##
=======================================
  Coverage   94.25%   94.25%           
=======================================
  Files          43       43           
  Lines       20487    20487           
=======================================
+ Hits        19309    19311    +2     
+ Misses       1178     1176    -2     

[tatsuya6502]

Merging.