Merge user-defined tags with default tags in stardoc macro (#247)
### Description
This pull request introduces changes to the `stardoc` macro to enhance its functionality by including user-defined tags in auxiliary targets. Previously, auxiliary targets only included default tags, and there was no way to specify additional tags.
### Changes Made
1. **Tag Handling:**
- **Update:** Modified the `stardoc` macro to merge user-defined tags with default tags for auxiliary targets.
- **Default Behavior:** By default, auxiliary targets receive the `["manual"]` tag.
- **User-defined Tags:** If user-defined tags are provided, they are appended to the default tag list.
2. **Code Modifications:**
- **File Updated:** `stardoc/stardoc.bzl`
- **Details:** Added logic to handle the merging of tags in the `stardoc` macro. Ensured that user-defined tags are correctly
combined with default tags before being applied to auxiliary targets.
Fixes #245 
Stardoc is a documentation generator for Bazel build rules written in Starlark.
Stardoc provides a Starlark rule (stardoc, see documentation) that can be used to build documentation for Starlark rules in Markdown. Stardoc generates one documentation page per .bzlfile.
Stardoc is a replacement for the deprecated “Skydoc” documentation generator.
See Skydoc Deprecation for details on the deprecation and migration details.
See our future plans for refactoring Stardoc to be more consistent with how Bazel evaluates .bzl files, and what it means for maintenance of this project.
See the maintaner's guide for instructions for cutting a new release.