feat: improve accessibility (ReVanced#64)

* Label Back button
* Mark group section headings as headings

Signed-off-by: Patryk Miś <foss@patrykmis.com>

Author: PatrykMis

app/src/main/java/app/revanced/manager/ui/component/AppScaffold.kt

@@ -8,7 +8,9 @@ import androidx.compose.material3.*
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.input.nestedscroll.nestedScroll
+import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.unit.dp
+import app.revanced.manager.R
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
@@ -47,7 +49,7 @@ fun AppTopBar(
                 IconButton(onClick = onBackClick) {
                     Icon(
                         imageVector = Icons.Default.ArrowBack,
-                        contentDescription = null
+                        contentDescription = stringResource(R.string.back)
                     )
                 }
             }

app/src/main/java/app/revanced/manager/ui/component/GroupHeader.kt

@@ -5,6 +5,8 @@ import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.semantics.heading
+import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.unit.dp
 
 @Composable
@@ -16,6 +18,6 @@ fun GroupHeader(
         text = title,
         color = MaterialTheme.colorScheme.primary,
         style = MaterialTheme.typography.labelLarge,
-        modifier = Modifier.padding(16.dp).then(modifier)
+        modifier = Modifier.padding(16.dp).semantics { heading() }.then(modifier)
     )
 }