Add 1.25.0 documentation (#289)

Reviewed-on: https://gitea.com/gitea/docs/pulls/289

versioned_docs/version-1.25/usage/actions/variables.md

@@ -0,0 +1,32 @@
+---
+date: "2024-04-10T22:21:00+08:00"
+slug: "actions-variables"
+sidebar_position: 25
+---
+
+# Variables
+
+You can create configuration variables on the user, organization and repository level.
+The level of the variable depends on where you created it. When creating a variable, the
+key will be converted to uppercase. You need use uppercase on the yaml file.
+
+## Naming conventions
+
+The following rules apply to variable names:
+
+- Variable names can only contain alphanumeric characters (`[a-z]`, `[A-Z]`, `[0-9]`) or underscores (`_`). Spaces are not allowed.
+- Variable names must not start with the `GITHUB_` and `GITEA_` prefix.
+- Variable names must not start with a number.
+- Variable names are case-insensitive.
+- Variable names must be unique at the level they are created at.
+- Variable names must not start with `CI`.
+
+## Using variable
+
+After creating configuration variables, they will be automatically filled in the `vars` context.
+They can be accessed through expressions like `${{ vars.VARIABLE_NAME }}` in the workflow.
+
+## Precedence
+
+If a variable with the same name exists at multiple levels, the variable at the lowest level takes precedence:
+A repository variable will always be chosen over an organization/user variable.