(chore): document and test new LogLevel APIs

- add godoc for SameLevel and Equal
- update package docs and READMEs with new helpers
- refresh unreleased release notes
- add tests for Printf, HTTP method levels, and level constructors

README.md

@@ -135,6 +135,23 @@ httpCache.SetForeground256Color(214)
 Because `LogLevel` setters mutate the level in place, call them on a variable, not on a temporary value returned by `NewLogLevel(...)`.
 Short forms such as `SetFgColor` and `SetBgColor` remain available for backward compatibility.
 
+Common severities also have dedicated helpers:
+
+```go
+access := sneklog.NewInfoLogLevelWithColors("access", sneklog.FgCyan, sneklog.BgNone)
+audit := sneklog.NewWarnLogLevel("audit")
+```
+
+HTTP method-specific predefined levels are available out of the box:
+
+```go
+level := sneklog.LogLevelForMethod(http.MethodPost)
+logger.Print(level, "POST /users")
+```
+
+When comparing levels, use `SameLevel` if only the severity matters and `Equal`
+if the full configuration, including colors and attributes, must match.
+
 ## Message replacement
 
 `AddReplacer(old, new)` replaces matching text in every message before the
@@ -157,6 +174,7 @@ An empty `old` value is ignored.
 
 - `Info`, `Warn`, `Error`, `Debug`, and `Fatal` accept a list of values.
 - `Infof`, `Warnf`, `Errorf`, `Debugf`, and `Fatalf` use `fmt.Sprintf`.
+- `Printf(level, format, args...)` formats a message for an explicit `LogLevel`.
 - The `*ln` methods preserve newline semantics, which is useful for `stdout`, Docker, and line-based collectors.
 - `Fatal`, `Fatalf`, and `Fatalln` call `os.Exit(1)` after writing the message.
 - `AddReplacer` masks or rewrites message text before records are sent to writers.