feat(ext): Replace shell select with input

It not of much help imposing this restriction if a user already chose
Custom. And this is probably also needed for it to work under Windows,
since most people don't put their bash.exe into system search path.

extension/options/options.html

@@ -46,13 +46,7 @@
     <tr id="shell-row" style="display: none;">
       <td><label>Shell</label></td>
       <td>
-        <select name="shell" id="shell">
-          <option value="sh">sh</option>
-          <option value="bash">bash</option>
-          <option value="ash">ash</option>
-          <option value="dash">dash</option>
-          <option value="dash">zsh</option>
-        </select>
+        <input name="shell" id="shell" type="text" value="sh" />
       </td>
     </tr>
     <tr id="template-row">

extension/options/options.js

@@ -18,7 +18,7 @@ const editorSelect = document.getElementById('editor')
 const terminalRow = document.getElementById('terminal-row')
 const terminalSelect = document.getElementById('terminal')
 const shellRow = document.getElementById('shell-row')
-const shellSelect = document.getElementById('shell')
+const shellInput = document.getElementById('shell')
 const templateInput = document.getElementById('template')
 const bypassVersionCheckInput = document.getElementById('bypass-version-check')
 const applyButton = document.getElementById('apply')
@@ -104,7 +104,7 @@ async function updateTemplate() {
 async function saveSettings() {
   const editor = editorSelect.value
   const terminal = terminalSelect.value
-  const shell = editor === 'custom' ? shellSelect.value : 'sh'
+  const shell = editor === 'custom' ? shellInput.value : 'sh'
   const template = templateInput.value
   const bypassVersionCheck = bypassVersionCheckInput.checked
   await browser.storage.local.set({
@@ -121,7 +121,7 @@ async function loadSettings() {
   if (settings.editor) {
     editorSelect.value = settings.editor
     terminalSelect.value = settings.terminal
-    shellSelect.value = settings.shell
+    shellInput.value = settings.shell
     templateInput.value = settings.template
     bypassVersionCheckInput.checked = settings.bypassVersionCheck
     updateOptionsForEditor(settings.editor)