Add 'What's an instance' dialog in login instead of opening link

app/src/main/java/com/h/pixeldroid/LoginActivity.kt

@@ -104,9 +104,13 @@ class LoginActivity : BaseActivity() {
 
 
     private fun whatsAnInstance() {
-        val i = Intent(Intent.ACTION_VIEW)
-        i.data = Uri.parse("https://pixelfed.org/join")
-        startActivity(i)
+        val builder = AlertDialog.Builder(this)
+        builder.apply {
+            setView(layoutInflater.inflate(R.layout.whats_an_instance_explanation, null))
+            setPositiveButton(android.R.string.ok) { _, _ -> }
+        }
+        // Create the AlertDialog
+        builder.show()
     }
 
     private fun hideKeyboard() {

app/src/main/java/com/h/pixeldroid/postCreation/carousel/ImageCarousel.kt

@@ -454,8 +454,10 @@ class ImageCarousel(
 
                         dataItem?.apply {
                             caption.apply {
-                                binding.editMediaDescriptionLayout.visibility = INVISIBLE
-                                tvCaption.visibility = VISIBLE
+                                if(layoutCarousel){
+                                    binding.editMediaDescriptionLayout.visibility = INVISIBLE
+                                    tvCaption.visibility = VISIBLE
+                                }
                                 currentDescription = this
                             }
                         }

app/src/main/res/layout/whats_an_instance_explanation.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/whats_an_instance_explanation"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:autoLink="web"
+    android:padding="16dp"
+    android:text="@string/whats_an_instance_explanation" />

app/src/main/res/values/strings.xml

@@ -28,6 +28,13 @@
 
     <!-- Login page -->
     <string name="whats_an_instance">"What's an instance?"</string>
+    <string name="whats_an_instance_explanation">"You might be confused by the text field asking for the domain of your 'instance'.
+
+Pixelfed is a federated platform, and part of the 'fediverse', which means it can talk to other platforms which speak the same language, like Mastodon (see https://joinmastodon.org).
+
+It also means you have to choose which server, or 'instance' of Pixelfed to use. If you don't know any, you can look here: https://pixelfed.org/join
+
+For more info about Pixelfed, you can check here: https://pixelfed.org"</string>
     <string name="domain_of_your_instance">Domain of your instance</string>
     <string name="connect_to_pixelfed">Connect to Pixelfed</string>
     <string name="login_connection_required_once">You need to be online to be able to add the first account and use PixelDroid :(</string>