Update the default issue template

Change some of the headings and reduce the information while still keeping the same points to make it easier to skim and more likely to be read.

Author: rickhanlonii

.github/ISSUE_TEMPLATE/default.md

@@ -4,29 +4,28 @@ about: Start a new conversation about a broad topic for React Native
 ---
 
 <!--
-Hello there!
-Thanks for deciding to start a conversation about React Native and how it could evolve for the better!
+Thank you for starting a discussion about React Native!
 
-If possible, please follow the structure shown below (you can also take inspiration from other open issues).
+Please follow the structure shown below.
 
-Given the nature of this repository, ideally only long-form discussions should be held here in the issue section.
+Note: Issues should be limited to long-form discussions.
 If you have a proposal, please add it via a Pull Request.
 -->
 
 ### Introduction
 
 <!--
-Give a brief intro about the subject you want to discuss about
+A brief intro about the topic you want to discuss.
 -->
 
-### The Core of It
+### Details
 
 <!--
-Here you should explain in details what you want to discuss about, providing all the necessary details for everyone to understand
+Details about what you want to discuss.
 -->
 
 ### Discussion points
 
 <!--
-If you can, summarize the 'hot points' that you want the discussion to focus on
+Summarize the main points you want to focus the discussion on.
 -->