Update changelog

Author: ashao

doc/changelog.md

@@ -16,8 +16,13 @@ To be released at some point in the future
 Description
 
 - Add instructions for installing SmartSim on PML's Scylla
+- Update install notes and documentation for custom backends
 
 Detailed Notes
+- Update/reorganize the install instructions to include a split between advanced
+  install notes and instructions for specific platforms. Additionally, add
+  instructions for machines which do not have access to the internet.
+  ([SmartSim-PR749](https://github.com/CrayLabs/SmartSim/pull/749))
 - PML's Scylla is still under development. The usual SmartSim
   build instructions do not apply because the GPU dependencies
   have yet to be installed at a system-wide level. Scylla has

doc/index.rst

@@ -12,6 +12,7 @@
 
    overview
    installation_instructions/basic
+   installation_instructions/install_notes
    installation_instructions/platform
    contributing
    smartsim_zoo

doc/installation_instructions/platform.rst

@@ -1,18 +1,5 @@
-.. _install-notes:
-
-General Installation Notes
-==========================
-
-SmartSim has been installed on a variety of systems and our users often have
-different build environments and toolchains. The following two sections detail
-some common situations and how to setup and modify your build environment:
-
-.. include:: platform/generic.rst
-
-.. include:: platform/nonroot-linux.rst
-
-Installation guides for specific platforms
-==========================================
+Platform Install Guide
+======================
 
 HPC platforms have specific modules that users can often use so they do not
 need to retrieve all of the build dependencies themselves. Some machines