fixed some style issues, added tooling for docs

docs/core/logger.md

@@ -0,0 +1,13 @@
+# core/logger.h
+
+## class Logger — public interface
+
+### `Logger(std::string_view path, bool append) noexcept;`
+### `~Logger() noexcept;`
+### `Logger(const Logger &) = delete;`
+### `Logger(Logger &&) = delete;`
+### `bool is_open() const noexcept { ... }`
+### `void write_line(std::string_view line) noexcept;`
+### `void flush() noexcept;`
+### `void close() noexcept;`
+### `std::string_view path() const noexcept { ... }`