Custom vendor dirs

[mikepqr]

I have several directory/sentinels I would like to exclude that are not generally applicable. This raises the possibility of a per-user configuration file whose contents get appended to ASIMOV_VENDOR_DIR_SENTINELS. Something like:

diff --git a/asimov b/asimov
index 81df4a7..e963344 100755
--- a/asimov
+++ b/asimov
@@ -19,6 +19,8 @@ set -Eeu -o pipefail

 readonly ASIMOV_ROOT=~

+readonly ASIMOV_CUSTOM_VENDOR_DIR_FILE="${HOME}/.config/asimov"
+
 # Paths to unconditionally skip over. This prevents Asimov from modifying the
 # Time Machine exclusions for these paths (and decendents). It has an important
 # side-effect of speeding up the search.
@@ -33,7 +35,7 @@ readonly ASIMOV_SKIP_PATHS=(
 #
 # For example, 'node_modules package.json' means "exclude node_modules/ from the
 # Time Machine backups if there is a package.json file next to it."
-readonly ASIMOV_VENDOR_DIR_SENTINELS=(
+readonly ASIMOV_DEFAULT_VENDOR_DIR_SENTINELS=(
     '.build Package.swift'             # Swift
     '.gradle build.gradle'             # Gradle
     '.gradle build.gradle.kts'         # Gradle Kotlin Script
@@ -72,6 +74,17 @@ readonly ASIMOV_VENDOR_DIR_SENTINELS=(
     'cdk.out cdk.json'                 # AWS CDK
 )

+if [ -f "$ASIMOV_CUSTOM_VENDOR_DIR_FILE" ]; then
+    mapfile -t ASIMOV_CUSTOM_VENDOR_DIR_SENTINELS <"$ASIMOV_CUSTOM_VENDOR_DIR_FILE"
+else
+    readonly ASIMOV_CUSTOM_VENDOR_DIR_SENTINELS=()
+fi
+
+readonly ASIMOV_VENDOR_DIR_SENTINELS=(
+    "${ASIMOV_DEFAULT_VENDOR_DIR_SENTINELS[@]}"
+    "${ASIMOV_CUSTOM_VENDOR_DIR_SENTINELS[@]}"
+)
+
 # Exclude the given paths from Time Machine backups.
 # Reads the newline-separated list of paths from stdin.
 exclude_file() {

This needs some work (e.g. validation of the contents of the configuration file), documentation, etc. but would you take a PR along these lines? Any comments on what I have so far?