chore: update PR template (#32011)

Author: mdrxy

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,28 +1,34 @@
 Thank you for contributing to LangChain!
 
-- [ ] **PR title**: "package: description"
-  - Where "package" is whichever of langchain, core, etc. is being modified. Use "docs: ..." for purely docs changes, "infra: ..." for CI changes.
-  - Example: "core: add foobar LLM"
-
+- [ ] **PR title**: Follows the [Conventional Commits specification](https://www.conventionalcommits.org/en/v1.0.0/): {TYPE}({SCOPE}): {DESCRIPTION}
+    - The `{DESCRIPTION}` must not start with an uppercase letter.
+    - Examples:
+        - feat(core): add multi-tenant support
+        - fix(cli): resolve flag parsing error
+        - docs(openai): update API usage examples
+    - Allowed `{TYPE}` values:
+        - feat, fix, docs, style, refactor, perf, test, build, ci, chore, revert, release
+    - Allowed `{SCOPE}` values (optional):
+        - core, cli, langchain, standard-tests, docs, anthropic, chroma, deepseek, exa, fireworks, groq, huggingface, mistralai, nomic, ollama, openai, perplexity, prompty, qdrant, xai
 
 - [ ] **PR message**: ***Delete this entire checklist*** and replace with
-    - **Description:** a description of the change
+    - **Description:** a description of the change. Include a [closing keyword](https://docs.github.com/en/issues/tracking-your-work-with-issues/using-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword) if applicable.
     - **Issue:** the issue # it fixes, if applicable
     - **Dependencies:** any dependencies required for this change
     - **Twitter handle:** if your PR gets announced, and you'd like a mention, we'll gladly shout you out!
 
 
 - [ ] **Add tests and docs**: If you're adding a new integration, please include
-  1. a test for the integration, preferably unit tests that do not rely on network access,
-  2. an example notebook showing its use. It lives in `docs/docs/integrations` directory.
+  1. A test for the integration, preferably unit tests that do not rely on network access,
+  2. An example notebook showing its use. It lives in `docs/docs/integrations` directory.
 
 
-- [ ] **Lint and test**: Run `make format`, `make lint` and `make test` from the root of the package(s) you've modified. See contribution guidelines for more: https://python.langchain.com/docs/contributing/
+- [ ] **Lint and test**: Run `make format`, `make lint` and `make test` from the root of the package(s) you've modified. We will not consider a PR unless these three are passing in CI. See contribution guidelines for more: https://python.langchain.com/docs/contributing/
 
 Additional guidelines:
 - Make sure optional dependencies are imported within a function.
-- Please do not add dependencies to pyproject.toml files (even optional ones) unless they are required for unit tests.
+- Please do not add dependencies to `pyproject.toml` files (even optional ones) unless they are **required** for unit tests.
 - Most PRs should not touch more than one package.
 - Changes should be backwards compatible.
 
-If no one reviews your PR within a few days, please @-mention one of baskaryan, eyurtsev, ccurme, vbarda, hwchase17.
+If no one reviews your PR within a few days, please @-mention one of eyurtsev, ccurme, mdrxy.