Fix shebang lines for a few scripts — radicle-explorer

On the BSDs, bash is typically installed in /usr/local/bin.

 #!/bin/bash
 #!/usr/bin/env bash
 set -Eeuo pipefail
 echo "Copying katex assets into bundle directory"

 #!/bin/bash
 #!/usr/bin/env bash
 set -e
 REPO_ROOT=$(git rev-parse --show-toplevel 2>/dev/null || echo "$PWD")

 #!/bin/bash
 #!/usr/bin/env bash
 set -Eeou pipefail
 version="$(node -e 'console.log(require("twemoji/package.json").version)')"