Update README.md

[davep]

Thanks. Once again, as mentioned in #12, I'd prefer to keep this list focused on Textual. While there is one item on that list that doesn't have an immediate dependency on Textual, it is there as it has a very direct benefit in Textual applications. I don't wish to turn this into a list that's outside of the original intended scope.

[pom11]

so creating templates/placeholders like in jinja doesnt benefit textual?

from textual.reactive import reactive
from textual.app import App, ComposeResult
from textual.widgets import Footer
from textual.widgets import Static
from rich.text import Text
import rich_format
import random

city = [
    Text.from_markup("from [blue on red]London[/]"),
    Text.from_markup("from [magenta on blue]New York[/]"),
    Text.from_markup("from [green]Bucharest[/]"),
    Text.from_markup("from [red on white]Tokyo[/]")
]

class CustomHeader(Static):
    banner : Text = reactive(Text(""))
    world : str = reactive("")

    def __init__(self, template: str) -> None:
        self.template = template
        super().__init__()

    def watch_banner(self, banner: Text) -> None:
        self.update(banner)

    def watch_world(self, world: str) -> None:
        self.banner = Text(self.template).format(world=world)

class DemoApp(App):

    BINDINGS = [
    ("q","quit","Quit"),
    ("h", "toggle_header", "Random header")
    ]

    def compose(self) -> ComposeResult:
        yield CustomHeader(template="Hello {world}")
        yield Footer()

    def action_toggle_header(self) -> None:
        widget = self.query_one(CustomHeader)
        widget.world = random.choice(city)

if __name__ == '__main__':
    app = DemoApp()
    app.run()