Fix shebangs in .sh files

ci/install_cargo_web.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 set -euo pipefail
 IFS=$'\n\t'

ci/run_tests.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # Originally this ci script borrowed from https://github.com/koute/stdweb
 # because both use `cargo-web` tool to check the compilation.

examples/build_all.sh

@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 PID=-1
 
 function ctrl_c() {