[FIX] web_editor: detect spaces correctly

Because of css rules, when a space was inserted (which is supposed to close the power box), it wouldn't be present in the innerText string.
It was fixed by using the textContent property instead, which contains all the spaces, including the invisible ones.
This might cause problems in some situation where the markup that the editor is modifying contains formatting spaces.

task-2584101

closes odoo/odoo#74766

Signed-off-by: Antoine Guenet <Zinston@users.noreply.github.com>

addons/web_editor/static/lib/odoo-editor/src/powerbox/Powerbox.js

@@ -170,7 +170,7 @@ export class Powerbox {
             this.show();
             openOnKeyupTarget.removeEventListener('keyup', showOnceOnKeyup, true);
             initialTarget = openOnKeyupTarget;
-            this._initialValue = openOnKeyupTarget.innerText;
+            this._initialValue = openOnKeyupTarget.textContent;
         };
         openOnKeyupTarget.addEventListener('keyup', showOnceOnKeyup, true);
 
@@ -188,7 +188,7 @@ export class Powerbox {
             if (!initialTarget) return;
             const diff = patienceDiff(
                 this._initialValue.split(''),
-                initialTarget.innerText.split(''),
+                initialTarget.textContent.split(''),
                 true,
             );
             this._lastText = diff.bMove.join('');
@@ -284,7 +284,7 @@ export class Powerbox {
         this._currentOpenOptions = openOptions;
         this._initialValue = (
             this._currentOpenOptions.openOnKeyupTarget || this.options.editable
-        ).innerText;
+        ).textContent;
         this._currentFilteredCommands = this._currentOpenOptions.commands;
         this.render(this._currentOpenOptions.commands);
     }