Add extensions, refactor context and request-related

[Desiders]

• Add Extension as in axum to save data without key, just by type. It's more convenient an analogue of the context because it can be extracted without implementations of Extractor.
  Example of usage and registration: https://github.com/Desiders/telers/blob/dev-1.x/examples/extractor/src/main.rs#L130, https://github.com/Desiders/telers/blob/dev-1.x/examples/extractor/src/main.rs#L145.

• Refactor Context to be easier to use: now you shouldn't to wrap any value to Box at insert, it's wrapped by the library. Typecast in user side removed, all methods like get already does it.
  
  Don't forget to change all insert calls to remove Box because otherwise typecast fail (it will be saved as Box<Box<...>>).

Code example:

// instead of `context.insert("url", Box::new(url.into_boxed_str()));`
context.insert("url", url.into_boxed_str());
// instead of `context.get("url").unwrap().downcast_ref::<Box<str>>();`
context.get::<Box<str>>("url");

• Refactor path and usage of Request in middlewares and filters.
  
  Now all data like context and extractors will be passed in request for filters and middlewares instead of pass them in different arguments:

New filter:

fn lowercase_filter(request: &mut Request) -> impl Future<Output = bool> {
    let result = request
        .update
        .text()
        .map_or(false, |text| text.to_lowercase() == text);

    async move { result }
}

Old filter:

fn lowercase_filter(_bot: &Bot, update: &Update, _context: &Context) -> impl Future<Output = bool>
{
    let result = update
        .text()
        .map_or(false, |text| text.to_lowercase() == text);

    async move { result }
}

As you can see, there also added &mut, so you can without any problems change the request (there no Arc now)

• Rename FromEventAndContext to Extractor and HandlerObject to HandlerComposition
• Docs small fixes
• Update MSRV to 1.71.1
• Change path of telers::{router/...}::Request to telers::Request