add a gaussian 16 example (#193)

* add a g16 example

* fix grammar

Author: njzjz

doc/examples/g16.md

@@ -0,0 +1,10 @@
+# Running Gaussian 16 with failure allowed
+
+Typically, a task will retry three times if the exit code is not zero. Sometimes, one may allow non-zero code. For example, when running large amounts of Gaussian 16 single-point calculation tasks, some of the Gaussian 16 tasks may throw SCF errors and return a non-zero code. One can append `||:` to the command:
+
+```{literalinclude} ../../examples/task/g16.json
+:language: json
+:linenos:
+```
+
+This command ensures the task will always provide zero code.

examples/task/g16.json

@@ -0,0 +1,10 @@
+{
+    "command": "g16 < input > output ||:",
+    "task_work_path": "p1/",
+    "forward_files": [
+      "input"
+    ],
+    "backward_files": [
+      "output"
+    ]
+}