Change cloned entity's last-modified date to the date it was cloned

Thanks for the quick response. Very good that it's optional and it does what this issue was requesting.

A remark concerning the concept:

• If we make 'resetting the modified date' optional, wouldn't it make more sense to make the created date optional together with the modified date? The modified date should always be equal or later than the created date anyways. So seeing this patch, I would change the option to "Set the created and modified date to the current date" (or something similar to that). I can imagine that some cases require both dates to stay the same. But never to have an updated 'created date' and an optional old 'last modified' date. My 2 cents.

Some small styling remarks:

1. +++ b/src/EntityClone/Content/ContentEntityCloneBase.php
   @@ -112,6 +112,11 @@ class ContentEntityCloneBase implements EntityHandlerInterface, EntityCloneInter
   +    //Updates last-modified date of cloned entity if option is checked.
   

   Set a space after the comment slashes.

2. +++ b/src/Form/EntityCloneForm.php
   @@ -166,6 +166,13 @@ class EntityCloneForm extends FormBase {
   +        '#title' => $this->stringTranslationManager->translate('Update "Last-Modified".'),
   

   No period sign required for the checkbox label.

3. +++ b/src/Form/EntityCloneForm.php
   @@ -166,6 +166,13 @@ class EntityCloneForm extends FormBase {
   +        '#description' => $this->stringTranslationManager->translate('Updates "last modified" date of newly created cloned entity'),
   

   A period sign is required for the description sentence.

4. +++ b/src/Form/EntityCloneSettingsForm.php
   @@ -118,6 +118,13 @@ class EntityCloneSettingsForm extends ConfigFormBase implements ContainerInjecti
   +      '#title' => $this->t('Updates "last-modified" date to the cloning date.'),
   

   No period sign is required for the checkbox label.

5. +++ b/src/Form/EntityCloneSettingsForm.php
   @@ -118,6 +118,13 @@ class EntityCloneSettingsForm extends ConfigFormBase implements ContainerInjecti
   +      '#description' => $this->t('Wheter the "Update last-modified" option should be checked by default on the entity clone form.'),
   

   Typo: wheter => whether