Add functionSignatures.json

Cf. https://www.mathworks.com/help/matlab/matlab_prog/customize-code-suggestions-and-completions.html
for details about the file format.

JSON unfortunately does not allow comments. Some of the "type" definitions in
the file do not match accepted values exactly: I have not listed that several
name value pairs accept empties, and have not found a good way to say that
StopSequences can have at most four entries. Nothing in here removes the
existing input validations.

functionSignatures.json

@@ -0,0 +1,43 @@
+{
+	"_schemaVersion": "1.0.0",
+	"openAIChat.openAIChat":
+	{
+		"inputs":
+		[
+			{"name":"systemPrompt","kind":"ordered","type":["string","scalar"]},
+			{"name":"Tools","kind":"namevalue","type":"openAIFunction"},
+			{"name":"ModelName","kind":"namevalue","type":"choices=llms.openai.models"},
+			{"name":"Temperature","kind":"namevalue","type":["numeric","scalar",">=0","<=2"]},
+			{"name":"TopProbabilityMass","kind":"namevalue","type":["numeric","scalar",">=0","<=1"]},
+			{"name":"StopSequences","kind":"namevalue","type":["string","vector"]},
+			{"name":"ResponseFormat","kind":"namevalue","type":"choices={'text','json'}"},
+			{"name":"ApiKey","kind":"namevalue","type":["string","scalar"]},
+			{"name":"PresencePenalty","kind":"namevalue","type":["numeric","scalar","<=2",">=-2"]},
+			{"name":"FrequencyPenalty","kind":"namevalue","type":["numeric","scalar","<=2",">=-2"]},
+			{"name":"TimeOut","kind":"namevalue","type":["numeric","scalar","real","positive"]},
+			{"name":"StreamFun","kind":"namevalue","type":"function_handle"}
+		],
+		"outputs":
+		[
+			{"name":"this","type":"openAIChat"}
+		]
+	},
+	"openAIChat.generate":
+	{
+		"inputs":
+		[
+			{"name":"this","kind":"required","type":["openAIChat","scalar"]},
+			{"name":"messages","kind":"required","type":[["openAIMessages","row"],["string","scalar"]]},
+			{"name":"NumCompletions","kind":"namevalue","type":["numeric","scalar","integer","positive"]},
+			{"name":"MaxNumTokens","kind":"namevalue","type":["numeric","scalar","positive"]},
+			{"name":"ToolChoice","kind":"namevalue","type":"choices=[\"none\",\"auto\",this.FunctionNames]"},
+			{"name":"Seed","kind":"namevalue","type":["numeric","integer","scalar"]}
+		],
+		"outputs":
+		[
+			{"name":"text","type":"string"},
+			{"name":"message","type":"struct"},
+			{"name":"response","type":"matlab.net.http.ResponseMessage"}
+		]
+	}
+}