Create lib finalize hook

Create an array `_bash_it_library_finalize_hook` and loop at the end of the main `bash_it.sh` to run each element in the array.

The purpose here is to run some command after everything else has been loaded. For example, the appearance lib checks for executables for SCM commands, but `$PATH` may be altered after appearance has loaded and therefore some available commands may never be discovered. Therefore, create `_bash_it_appearance_scm_init()` and add it to the hook. It will re-check at end of `bash_it.sh` just before prompt is first displayed.

bash_it.sh

@@ -15,8 +15,11 @@ fi
 # shellcheck disable=SC1090
 source "${BASH_IT}"/vendor/github.com/erichs/composure/composure.sh
 
-# We need to load logging module first as well in order to be able to log
-# shellcheck source=./lib/log.bash
+# Declare our end-of-main finishing hook
+declare -a _bash_it_library_finalize_hook
+
+# We need to load logging module early in order to be able to log
+# shellcheck source-path=SCRIPTDIR/lib
 source "${BASH_IT}/lib/log.bash"
 
 # We can only log it now
@@ -148,3 +151,8 @@ if ! _command_exists reload && [[ -n "${BASH_IT_RELOAD_LEGACY:-}" ]]; then
 			;;
 	esac
 fi
+
+for _bash_it_library_finalize_f in "${_bash_it_library_finalize_hook[@]:-}"; do
+	eval "${_bash_it_library_finalize_f?}" # Use `eval` to achieve the same behavior as `$PROMPT_COMMAND`.
+done
+unset "${!_bash_it_library_finalize_@}"

themes/base.theme.bash

@@ -106,7 +106,7 @@ function _bash_it_appearance_scm_init() {
 		fi
 	fi
 }
-_bash_it_appearance_scm_init
+_bash_it_library_finalize_hook+=('_bash_it_appearance_scm_init')
 
 function scm {
 	if [[ "$SCM_CHECK" = false ]]; then