Make compatible with ruby v3+

[Smolations]

The resolution of this issue allowed for a clean install/generation of cheatsets for ruby v2+. However, attempting to install the gem in ruby 3.2.2 resulted in some native extension build errors for nokogiri/nokogumbo and sqlite3 (and yes, I installed xcode CL tools). I haven't had time to mess with different versions yet, but most posts I find online that have similar build failures almost always include updating libraries in order to eliminate the errors.

$ gem install cheatset
Fetching sanitize-5.2.3.gem
Fetching sqlite3-1.3.13.gem
Fetching unindent-1.0.gem
Fetching haml-5.2.2.gem
Fetching nokogumbo-2.0.5.gem
Fetching redcarpet-3.6.0.gem
Fetching plist-3.7.0.gem
Fetching rouge-3.30.0.gem
Fetching cheatset-1.4.8.gem
Successfully installed unindent-1.0
Building native extensions. This could take a while...
ERROR:  Error installing cheatset:
	ERROR: Failed to build gem native extension.

    current directory: /Users/user/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/sqlite3-1.3.13/ext/sqlite3
/Users/user/.rbenv/versions/3.2.2/bin/ruby extconf.rb
checking for sqlite3.h... yes
checking for pthread_create() in -lpthread... yes
checking for sqlite3_libversion_number() in -lsqlite3... yes
checking for rb_proc_arity()... yes
checking for rb_integer_pack()... yes
checking for sqlite3_initialize()... yes
checking for sqlite3_backup_init()... yes
checking for sqlite3_column_database_name()... yes
checking for sqlite3_enable_load_extension()... no
checking for sqlite3_load_extension()... no
checking for sqlite3_open_v2()... yes
checking for sqlite3_prepare_v2()... yes
checking for sqlite3_int64 in sqlite3.h... yes
checking for sqlite3_uint64 in sqlite3.h... yes
creating Makefile

current directory: /Users/user/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/sqlite3-1.3.13/ext/sqlite3
make DESTDIR\= sitearchdir\=./.gem.20231120-29588-5dciji sitelibdir\=./.gem.20231120-29588-5dciji clean

current directory: /Users/user/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/sqlite3-1.3.13/ext/sqlite3
make DESTDIR\= sitearchdir\=./.gem.20231120-29588-5dciji sitelibdir\=./.gem.20231120-29588-5dciji
compiling backup.c
compiling database.c
database.c:60:3: error: call to undeclared function 'rb_check_safe_obj'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
  rb_check_safe_obj(file);
  ^
database.c:60:3: note: did you mean 'rb_check_safe_str'?
/Users/user/.rbenv/versions/3.2.2/include/ruby-3.2.0/ruby/internal/core/rstring.h:383:6: note: 'rb_check_safe_str' declared here
void rb_check_safe_str(VALUE);
     ^
database.c:201:18: warning: implicit conversion loses integer precision: 'long' to 'int' [-Wshorten-64-to-32]
  return INT2NUM((long)sqlite3_total_changes(ctx->db));
         ~~~~~~~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
database.c:233:3: warning: 'sqlite3_trace' is deprecated: first deprecated in macOS 10.12 [-Wdeprecated-declarations]
  sqlite3_trace(ctx->db, NIL_P(block) ? NULL : tracefunc, (void *)self);
  ^~~~~~~~~~~~~
  sqlite3_trace_v2
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/sqlite3.h:3222:36: note: 'sqlite3_trace' has been explicitly marked deprecated here
SQLITE_API SQLITE_DEPRECATED void *sqlite3_trace(
                                   ^
database.c:242:67: warning: implicit conversion loses integer precision: 'long' to 'int' [-Wshorten-64-to-32]
  VALUE result = rb_funcall(handle, rb_intern("call"), 1, INT2NUM((long)count));
                                                          ~~~~~~~ ^~~~~~~~~~~
database.c:310:14: error: call to undeclared function 'rb_tainted_str_new2'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
      return rb_tainted_str_new2((const char *)sqlite3_value_text(val));
             ^
database.c:320:14: error: call to undeclared function 'rb_tainted_str_new'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
      return rb_tainted_str_new((const char *)sqlite3_value_blob(val), len);
             ^
database.c:552:18: warning: implicit conversion loses integer precision: 'long' to 'int' [-Wshorten-64-to-32]
  return INT2NUM((long)sqlite3_errcode(ctx->db));
         ~~~~~~~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4 warnings and 3 errors generated.
make: *** [database.o] Error 1

make failed, exit code 2

Gem files will remain installed in /Users/user/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/sqlite3-1.3.13 for inspection.
Results logged to /Users/user/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/extensions/arm64-darwin-22/3.2.0/sqlite3-1.3.13/gem_make.out