Missing Support for the value Attribute

Description

This PR addresses Issue #428. The problem was that binding a signal to the defaultValue (or value) attribute of progress bars had no effect, preventing them from switching between determinate and indeterminate states as expected.

To resolve this, we have added a manual definition for the value attribute in our DSL—similar to the definition for the style attribute. This ensures that progress bars correctly update their state based on the underlying signal.

Reproduction

Below is a full reproduction snippet that demonstrates the issue (with no hacks):

import calico.IOWebApp
import calico.html.HtmlAttr
import calico.html.io.*
import calico.html.io.given
import cats.effect.IO
import cats.effect.kernel.Resource
import fs2.concurrent.SignallingRef
import fs2.dom.HtmlElement

object App extends IOWebApp {

  def render: Resource[IO, HtmlElement[IO]] = SignallingRef[IO].of(false).toResource.flatMap { ref =>
    div(
      progressTag(
        maxAttr := "100",
        value <-- ref.map {
          case true  => Some("20")
          case false => None
        }
      ),
      button("switch determinate/nondeterminate", onClick(ref.update(!_)))
    )
  }
}

When the signal toggles, the progress bar should switch between having a value (determinate state) and having no value (indeterminate state). However, due to missing support for the native value attribute, this behavior was not working as intended.

Changes Made

Manual value Attribute Definition:
Added a manual definition in the DSL (e.g., in calico/html/Html.scala) as follows:

def valueAttr: HtmlAttr[F, String] =
  HtmlAttr("value", encoders.identity)

This ensures that our DSL now has a dedicated valueAttr that correctly maps the value attribute to the native DOM property.