Shell style for multi-stage pipeline with heredoc

Please update the Shell Style guide to indicate which of the following 3 approaches for a multi-stage pipeline with heredoc is recommended:

### Approach 1

```bash
cat <<'EOF' \
| cat \
| cat \
| cat
hello
EOF
```

### Approach 2

```bash
cat <<'EOF' |
hello
EOF
cat \
| cat \
| cat
```

### Approach 3

```bash
(
cat \
| cat \
| cat \
| cat
) <<'EOF'
hello
EOF
```

Discussion: https://stackoverflow.com/questions/7046381