v1.11.1-rc5

• Fixed stlsoft::basic_simple_string<>#resize() — expanding a non-empty string no longer over-reads the source buffer (MinGW unit-test segfault in test.unit.stlsoft.string.simple_string);
• Converted CHANGES.txt to CHANGES.md and removed HISTORY.md;
• Project documentation modernisation — README.md, FAQ.md, INSTALL.md, EXAMPLES.md, KNOWN_ISSUES.md, TODO.md, HOW_YOU_CAN_HELP.md, AUTHORS.md; repository URLs STLSoft-1.11 → STLSoft;
• EXAMPLES.md — replaced “T.B.C.” placeholders with concrete summaries;
• README.md — fleshed out Components (sub-projects / libraries); CI badge targets ci.yml; badge set standardised;
• CI (ci.yml) — concurrency cancel-in-progress; branch triggers include dev / rc* / update; matrix cell order;
• CMake — minimum version 3.20; BUILD_TESTING option; project homepage URL; patch/revision version regex;
• Project boilerplate — .gitattributes, .vimrc, .vscode/settings.json;
• test.unit.versions — aligned with 1.11.1-rc5 (_STLSOFT_VER_1_11_1_RC5);