build: use /bin/sh instead of /bin/bash for shell

Running docker/build-push-action@v3 failed, as Alpine Linux
does not have /bin/bash, only /bin/sh,
see: https://github.com/aloisklink/mermaid-cli/runs/6854319356

This also changes the BASH only [[ "$OUTPUT" == "$EXPECTED_OUTPUT" ]]
in `run-tests.sh` into `[ "$OUTPUT" = "$EXPECTED_OUTPUT" ]`, which
should work in all POSIX shells.

copy_modules.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 cp ./node_modules/mermaid/dist/mermaid.min.js .
 
 mkdir -p fontawesome/css/

install-dependencies.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 # Install chromium and required fonts
 # available fonts https://wiki.alpinelinux.org/wiki/Fonts

package.json

@@ -14,9 +14,9 @@
   },
   "exports": "./src/index.js",
   "scripts": {
-    "upgrade": "yarn-upgrade-all && bash copy_modules.sh",
-    "prepare": "bash copy_modules.sh",
-    "prepack": "bash copy_modules.sh",
+    "upgrade": "yarn-upgrade-all && sh copy_modules.sh",
+    "prepare": "sh copy_modules.sh",
+    "prepack": "sh copy_modules.sh",
     "test": "standard && yarn node --experimental-vm-modules $(yarn bin jest)",
     "lint": "standard",
     "lint-fix": "standard --fix"

run-tests.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 INPUT_DATA=$1
 IMAGETAG=$2
 
@@ -33,7 +33,7 @@ cat $INPUT_DATA/flowchart1.mmd | docker run --rm -i -v $(pwd):/data $IMAGETAG -o
 # Test if mmdc crashes on Markdown files containing no mermaid charts
 OUTPUT=$(docker run --rm -v $(pwd):/data $IMAGETAG -i /data/test-positive/no-charts.md)
 EXPECTED_OUTPUT="No mermaid charts found in Markdown input"
-[[ "$OUTPUT" == "$EXPECTED_OUTPUT" ]] || echo "Expected output to be '$EXPECTED_OUTPUT', got '$OUTPUT'"
+[ "$OUTPUT" = "$EXPECTED_OUTPUT" ] || echo "Expected output to be '$EXPECTED_OUTPUT', got '$OUTPUT'"
 
 # Test if mmdc does not replace <br> with <br/>
 docker run --rm -v $(pwd):/data $IMAGETAG -i /data/test-positive/graph-with-br.mmd -w 800;