Update upgrading.md

Adding a general statement at the top based on questions we sometimes get about whether these instructions still apply and whether someone has to upgrade to all versions in between to get to a later version.

src/content/docs/administration/upgrading.md

@@ -2,10 +2,13 @@
 title: Upgrading to a new release
 ---
 
+You can upgrade most versions of ArchivesSpace to a later version using these general instructions. Typically you do not need to progress through other versions of ArchivesSpace to get to a later one, unless there are special considerations for a specific version. Special considerations for these versions are noted here and in release notes.
+
 - **[Special considerations when upgrading to v1.1.0](/administration/upgrading_1_1_0)**
 - **[Special considerations when upgrading to v1.1.1](/administration/upgrading_1_1_1)**
 - **[Special considerations when upgrading from v1.4.2 to 1.5.x (these considerations also apply when upgrading from 1.4.2 to any version through 2.0.1)](/administration/upgrading_1_5_0)**
 - **[Special considerations when upgrading to 2.1.0](/administration/upgrading_2_1_0)**
+- **[Changing to external Solr when upgrading to 3.2.0 or later versions](https://docs.archivesspace.org/provisioning/solr/).**
 
 ## Create a backup of your ArchivesSpace instance