Added pull request template to facilitate standardized contributions.

Signed-off-by: Leander Stephen D'Souza <leanderdsouza1234@gmail.com>

Author: leander-dsouza

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,25 @@
+<!-- Please fill out the following pull request template for non-trivial changes to help us process your PR faster and more efficiently.-->
+
+---
+
+## Basic Info
+
+| Info | Please fill out this column |
+| ------ | ----------- |
+| Ticket(s) this addresses   | (add tickets here #1 or N/A) |
+| Nav2 Ticket(s) this addresses   | (paste the link of ros-navigation/navigation2 PR here or N/A) |
+---
+
+## Description of contribution in a few bullet points
+
+<!--
+* Updated the documentation to reflect corresponding changes in navigation2.
+* Reorganised some sections for better clarity.
+-->
+
+## Description of how this change was tested
+
+<!--
+* Performed linting validation using `pre-commit run --all`.
+* Tested that the website builds locally using `make html`.
+-->