Search for users to start a new DM. (#376)

Search for users to start a new DM.

Hooks up the create room UI to the matrix client to get
search results. Searches are debounced for 500ms and
only executed when 3 or more characters are entered.

Wrap the result state so we can distinguish between
"no results because we haven't searched yet" and
"no results because the API returned nothing", and
add a "No results found" message in the UI for the
latter case.

Closes #95

features/userlist/api/build.gradle.kts

@@ -15,6 +15,7 @@
  */
 plugins {
     id("io.element.android-compose-library")
+    alias(libs.plugins.ksp)
 }
 
 android {
@@ -27,4 +28,5 @@ dependencies {
     implementation(projects.libraries.uiStrings)
     implementation(projects.libraries.matrix.api)
     implementation(projects.libraries.matrixui)
+    ksp(libs.showkase.processor)
 }