Fix incorrect editor style name for Unity 2022.3+

[Shimmermare]

In Unity 2022.3 they fixed typo in style name.
Unity-Technologies/UnityCsReference@da51b77#diff-d4e399fabac0c73f6f6580b4c4094492ab460619fb45fe621764230982beefd3

Closes #8

[Walter-Hulsebos]

In Unity's own repos they use this, we probably wanna match that

#if UNITY_2023_2_OR_NEWER || UNITY_2021_3_28 || UNITY_2022_3_1

[Shimmermare]

In Unity's own repos they use this, we probably wanna match that

#if UNITY_2023_2_OR_NEWER || UNITY_2021_3_28 || UNITY_2022_3_1

Good point. Though I don't think there are defines for UNITY_2021_3_28_OR_NEWER and UNITY_2022_3_1_OR_NEWER, so I replaced define checks with simple null check.

[hgrandry]

Hi. Any reason why this has not been merged?

I have created a fork of this repo to do the exact same fix and pull the fix from the package manager. I imagine a lot of people using this package with a somewhat recent version of Unity has the same problem (any version above ~2021.3.14 apparently).

Same for this PR on the UnityDropdown repo: SolidAlloy/UnityDropdown#2

[buzzrick]

+1 for merging this and the UnityDropdown one please. I was also in the process of forking to create the same fix before I realised it was already a PR.