direnv: add page (#4392)

pages/common/direnv.md

@@ -0,0 +1,24 @@
+# direnv
+
+> Shell extension to load and unload environment variables depending on the current directory.
+> More information: <https://github.com/direnv/direnv>.
+
+- Grant direnv permission to load the specified .envrc:
+
+`direnv allow`
+
+- Revoke the authorization of a given .envrc:
+
+`direnv deny`
+
+- Edit the `.envrc` file in the default text editor and reload the environment on exit:
+
+`direnv allow`
+
+- Trigger a reload of the environment:
+
+`direnv reload`
+
+- Print some debug status information:
+
+`direnv status`