Experimental TUI powered by Trogon

* sqlite-utils tui command if Trogon is installed, closes #545
* Documentation for trogon TUI
* Screenshot of TUI
* Ignore trogon mypy error
* only run flake8 on Python 3.8 or higher, closes #550

sqlite_utils/cli.py

@@ -33,6 +33,11 @@ from .utils import (
     TypeTracker,
 )
 
+try:
+    import trogon  # type: ignore
+except ImportError:
+    trogon = None
+
 
 CONTEXT_SETTINGS = dict(help_option_names=["-h", "--help"])
 
@@ -112,6 +117,10 @@ def cli():
     pass
 
 
+if trogon is not None:
+    cli = trogon.tui()(cli)
+
+
 @cli.command()
 @click.argument(
     "path",