Improve Dockerfile and compose.yaml

- Dockerfile:
  - Accept HOST_UID as an ARG and set a default value

- compose.yaml:
  - Persist /usr/local/bundle as a volume
  - Pass HOST_UID to avoid permission issues
  - Set a default value for HOST_UID if not provided
  - Update usage comments

Dockerfile

@@ -1,5 +1,6 @@
 FROM ruby:3.4.1-bookworm
-RUN useradd rurema --create-home --shell /bin/bash
+ARG HOST_UID=1000
+RUN useradd rurema -u ${HOST_UID} --create-home --shell /bin/bash
 USER rurema:rurema
 ENV BUNDLE_AUTO_INSTALL true
 WORKDIR /workspaces/doctree

compose.yaml

@@ -1,18 +1,25 @@
 # usage:
 #
-# docker compose build
+# docker compose build --build-arg HOST_UID=$(id -u)
 # docker compose run --rm rurema rake -T
-# docker compose run --rm rurema rake generate:2.7.0 statichtml:2.7.0
-# open _site/2.7.0/index.html instead of /tmp/html/2.7.0/index.html
+# docker compose run --rm rurema rake generate:3.4 statichtml:3.4
+# open _site/3.4/index.html instead of /tmp/html/3.4/index.html
 services:
   rurema:
-    build: .
+    build:
+      context: .
+      args:
+        HOST_UID: ${HOST_UID:-1000}
     volumes:
       - ..:/workspaces:cached
       - "./_site:/tmp/html/"
+      - "bundle_cache:/usr/local/bundle"
   web:
     image: nginx
     ports:
-    - "8080:80"
+      - "8080:80"
     volumes:
-    - "./_site:/usr/share/nginx/html:ro"
+      - "./_site:/usr/share/nginx/html:ro"
+
+volumes:
+  bundle_cache: