meta: add pull request template (#2762)

### Description
Adds a pull request template.

#### Issues
* resolves: #2742
* resolves: CLI-165

---------

Co-authored-by: Daniel Szoke <7881302+szokeasaurusrex@users.noreply.github.com>

Author: dingsdax

.github/pull_request_template.md

@@ -0,0 +1,18 @@
+### Description
+<!-- What changed and why? -->
+
+### Issues
+<!--
+* resolves: #1234
+* resolves: LIN-1234
+-->
+
+<!--
+#### Reminders
+- Add GH Issue ID _&_ Linear ID (if applicable)
+- PR title should use [conventional commit](https://develop.sentry.dev/engineering-practices/commit-messages/#type) style (`feat:`, `fix:`, `ref:`, `meta:`)
+- For external contributors: [CONTRIBUTING.md](https://github.com/getsentry/sentry-cli/blob/master/CONTRIBUTING.md), [Sentry SDK development docs](https://develop.sentry.dev/sdk/), [Discord community](https://discord.gg/Ww9hbqr)
+-->
+
+
+