[GOVCMSD8-609] Update webform 5.13.

[suhyeonh]

webform 5.13

Changes since 8.x-5.12:

#3136574 by jrockowitz: Allow file upload extension list to include commas
#3136423 by hocu: Replace w3schools examples with relevant MDN documentation page links
#3136232 by jrockowitz: Overriding required message for select other only applies to original field
#3136062 by jrockowitz, jibran: Element contains ignored/unsupported properties: #equal_stepwise_validate
#3134549 by bighappyface, jrockowitz: Success Messages For Remote Post Handler
#3135574 by jrockowitz: Counter Maximum JS does not match validation
#3135075 by AndrewsizZ, jrockowitz: Replace assertEqual() or assertSame() on two calls to count() with assertCount()
#3135006 by bighappyface: Webform Handler Token String Conversion Notice
#3135076 by AndrewsizZ: Replace assertions involving calls to is_array() with assertIsArray()/assertIsNotArray()
#3135070 by AndrewsizZ: Replace assert* involving an instanceof operator with assertInstanceOf()/assertNotInstanceOf()
#3135072 by AndrewsizZ: Replace assertions involving calls to file_exists with assertFileExists()/assertFileNotExists()
#3135160 by AndrewsizZ: Replace assertions involving calls to is_string() with assertIsString()/assertIsNotString()
#3135161 by AndrewsizZ: Replace assert*() involving equality comparison operators with assert(Not)(Equals|Same)
#3135164 by AndrewsizZ: Clean up all the remaining $this->assert()
#3134833 by jrockowitz: Subelement weight fails custom settings validation
#3119248 by jrockowitz, cleo7186: Editing Ajax Enabled Wizard Webform Shows Submit Button
#3134351 by Berdir: Notice: Undefined index: fieldname in ReferenceSelectWidget::formElement()
#3133393 by jrockowitz, Matthijs: Select widget of webform field doesn't use its entity reference selection plugin
#3134159 by jrockowitz: Custom composite - Files don't attach to email
#3132909 by jrockowitz: Adding a webform in an entity reference field (in a paragraph) fails
#3134367 by dennis_meuwissen: Respect an outgoing link's target when warning the user about unsaved changes in iOS
#3134439 by AndrewsizZ: Replace assertions involving calls to empty() with assertEmpty()/assertNotEmpty()/assertArrayNotHasKey()
#3134446 by AndrewsizZ: Replace assertions involving calls to isset() with assertArrayHasKey()/assertArrayNotHasKey
#3133271 by jrockowitz: Support NULL value when decoding YAML
#3134231 by jrockowitz: Notice: Trying to access array offset on value
#3134289 by jrockowitz: Cleanup ::getSortedDefinitions
#3132177 by jrockowitz: Allow custom YAML data in Remote post to be typecast
#3133208 by jrockowitz: Help text does not display before/after title on Email confirm element
#3133717 by jrockowitz: Custom third party settings are lost when General settings page is saved
#3133945 by douggreen: Remove .orig files accidentally committed
#3133888 by jrockowitz: Notice: Uninitialized string offset: 0 in Drupal\Core\Render\Element::property() (line 27 of core/lib/Drupal/Core/Render/Element.php)