Add hooks to check .sh and .bash headers - Fixes #1491 (#1765)

* Add hooks to check .sh and .bash headers
* Adds hooks/ to clean_files.txt

completion/available/cargo.completion.bash

@@ -1,5 +1,4 @@
-#!/usr/bin/env bash
-
+# shellcheck shell=bash
 # cargo (Rust package manager) completion
 
 if _binary_exists rustup && _binary_exists cargo; then

completion/available/knife.completion.bash

@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
 
 # Published originally as public domain code at https://github.com/wk8/knife-bash-autocomplete
 

completion/available/packer.completion.bash

@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
 cite "about-completion"
 about-completion "packer completion"
 

completion/available/pipx.completion.bash

@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
 # pipx completion
 
 if _command_exists register-python-argcomplete && _command_exists pipx; then

completion/available/rustup.completion.bash

@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
 
 # rustup (Rust toolchain installer) completion
 

completion/available/sdkman.completion.bash

@@ -1,3 +1,4 @@
+# shellcheck shell=bash
 _sdkman_complete() {
 	local CANDIDATES
 	local CANDIDATE_VERSIONS

completion/available/vault.completion.bash

@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
 cite "about-completion"
 about-completion "vault completion"