fix: source archive add subfolders (#3343)

`--add-file` adds only the `--prefix` joined with the basename of the added file, so, adding a folder like `vendor` would break havoc.

this basically writes our own source archives (which are more compressed) and allows to add an entire folder easily, as well as other mappings as `archives` already supports. 

refs #3102 #2911

Signed-off-by: Carlos A Becker <caarlos0@users.noreply.github.com>

www/docs/customization/source.md

@@ -25,7 +25,6 @@ source:
   prefix_template: '{{ .ProjectName }}-{{ .Version }}/'
 
   # Additional files/template/globs you want to add to the source archive.
-  # Will use --add-file of git-archive.
   # Defaults to empty.
   files:
     - LICENSE.txt
@@ -34,6 +33,22 @@ source:
     - docs/*
     - design/*.png
     - templates/**/*
+    # a more complete example, check the globbing deep dive below
+    - src: '*.md'
+      dst: docs
+      # Strip parent folders when adding files to the archive.
+      # Default: false
+      strip_parent: true
+      # File info.
+      # Not all fields are supported by all formats available formats.
+      # Defaults to the file info of the actual file if not provided.
+      info:
+        owner: root
+        group: root
+        mode: 0644
+        # format is `time.RFC3339Nano`
+        mtime: 2008-01-02T15:04:05Z
+
 ```
 
 !!! tip