chore: add language policy (#2987)

Author: mdrxy

.github/ISSUE_TEMPLATE/01-langchain.yml

@@ -4,6 +4,11 @@ title: "[langchain]: <Please write a comprehensive title>"
 labels: [langchain]
 
 body:
+  - type: markdown
+    attributes:
+      value: >
+        All contributions must be in English. See the
+        [language policy](https://docs.langchain.com/oss/python/contributing/overview#language-policy).
   - type: dropdown
     attributes:
       label: "Type of issue"

.github/ISSUE_TEMPLATE/02-langgraph.yml

@@ -4,6 +4,11 @@ title: "[langgraph]: <Please write a comprehensive title>"
 labels: [langgraph]
 
 body:
+  - type: markdown
+    attributes:
+      value: >
+        All contributions must be in English. See the
+        [language policy](https://docs.langchain.com/oss/python/contributing/overview#language-policy).
   - type: dropdown
     attributes:
       label: "Type of issue"

.github/ISSUE_TEMPLATE/03-langsmith.yml

@@ -4,6 +4,11 @@ title: "[langsmith]: <Please write a comprehensive title>"
 labels: [langsmith]
 
 body:
+  - type: markdown
+    attributes:
+      value: >
+        All contributions must be in English. See the
+        [language policy](https://docs.langchain.com/oss/python/contributing/overview#language-policy).
   - type: dropdown
     attributes:
       label: "Type of issue"

.github/ISSUE_TEMPLATE/04-reference-docs.yml

@@ -4,6 +4,11 @@ title: "[reference]: <Please write a comprehensive title>"
 labels: [reference]
 
 body:
+  - type: markdown
+    attributes:
+      value: >
+        All contributions must be in English. See the
+        [language policy](https://docs.langchain.com/oss/python/contributing/overview#language-policy).
   - type: dropdown
     attributes:
       label: "Type of issue"

.github/ISSUE_TEMPLATE/05-deepagents.yml

@@ -4,6 +4,11 @@ title: "[deepagents]: <Please write a comprehensive title>"
 labels: [deepagents]
 
 body:
+  - type: markdown
+    attributes:
+      value: >
+        All contributions must be in English. See the
+        [language policy](https://docs.langchain.com/oss/python/contributing/overview#language-policy).
   - type: dropdown
     attributes:
       label: "Type of issue"

.github/pull_request_template.md

@@ -28,7 +28,7 @@ Examples:
 
 ## Checklist
 <!-- Put an 'x' in all boxes that apply -->
-- [ ] I have read the [contributing guidelines](README.md)
+- [ ] I have read the [contributing guidelines](README.md), including the [language policy](https://docs.langchain.com/oss/python/contributing/overview#language-policy)
 - [ ] I have tested my changes locally using `docs dev`
 - [ ] All code examples have been tested and work correctly
 - [ ] I have used **root relative** paths for internal links