Python 3.15 released with frozendict, UTF-8 default and JIT gains

Python 3.15 has been released. Notable changes include the new sentinel and frozendict built-in types, UTF-8 as the default encoding, package start-up configuration files, and improvements to the experimental JIT compiler.

• New built-in sentinel and frozendict types added
• UTF-8 is now the default encoding
• Package start-up configuration files introduced
• Experimental JIT compiler improved