feat: impl docs (#4)

The entire public api is covered with documentation in two languages - Russian and English.

the library now supports the latest three versions of python - 3.12, 3.13 and 3.14

minor design changes: now, when a Boolean flag is entered, its value is an empty string, not None.

tests have been adapted to the supported versions of python, readmi has been redesigned in two languages, German is no longer available.

docs/code_snippets/response/snippet6.py

@@ -0,0 +1,38 @@
+from argenta import Command, Response, Router
+from argenta.command import Flag, Flags
+from argenta.command.flag import ValidationStatus
+from argenta.response import ResponseStatus
+
+router = Router(title="Flags Example")
+
+
+@router.command(
+    Command(
+        "process",
+        description="Process with flags",
+        flags=Flags([
+            Flag("format", possible_values=["json", "xml"]), 
+            Flag("verbose")
+        ]),
+    )
+)
+def process_handler(response: Response):
+    print(f"Status: {response.status}")
+
+    format_flag = response.input_flags.get_flag_by_name("format")
+    verbose_flag = response.input_flags.get_flag_by_name("verbose")
+
+    if format_flag:
+        format_value = format_flag.input_value
+        print(f"Format: {format_value}")
+
+    if verbose_flag:
+        print("Verbose mode enabled")
+
+    if response.status == ResponseStatus.ALL_FLAGS_VALID:
+        print("All flags are valid, proceeding...")
+    elif response.status == ResponseStatus.INVALID_VALUE_FLAGS:
+        print("Warning: Some flags have invalid values")
+        for flag in response.input_flags:
+            if flag.status == ValidationStatus.INVALID:
+                print(f"  Invalid flag: {flag.string_entity} = {flag.input_value}")