Fix doc MyGovernor example doesn't compile (#4282)

Co-authored-by: Francisco Giordano <fg@frang.io>

scripts/prepare-docs.sh

@@ -1,6 +1,7 @@
 #!/usr/bin/env bash
 
 set -euo pipefail
+shopt -s globstar
 
 OUTDIR="$(node -p 'require("./docs/config.js").outputDir')"
 
@@ -13,11 +14,13 @@ rm -rf "$OUTDIR"
 hardhat docgen
 
 # copy examples and adjust imports
-examples_dir="docs/modules/api/examples"
-mkdir -p "$examples_dir"
-for f in contracts/mocks/docs/*.sol; do
-  name="$(basename "$f")"
-  sed -e '/^import/s|\.\./\.\./|@openzeppelin/contracts/|' "$f" > "docs/modules/api/examples/$name"
+examples_source_dir="contracts/mocks/docs"
+examples_target_dir="docs/modules/api/examples"
+
+for f in "$examples_source_dir"/**/*.sol; do
+  name="${f/#"$examples_source_dir/"/}"
+  mkdir -p "$examples_target_dir/$(dirname "$name")"
+  sed -e '/^import/s|\.\./\.\./|@openzeppelin/contracts/|' "$f" > "$examples_target_dir/$name"
 done
 
 node scripts/gen-nav.js "$OUTDIR" > "$OUTDIR/../nav.adoc"