Internal: Support multiple parameters for variables

[Taitava]

Current rules for {{variable}} parameters:

• A {{variable}} can have only one parameter ({{variable:parameter}}) or no paramers ({{variable}}).
• If a {{variable}} has a parameter, it's always mandatory, there's no way to define that a parameter could be left out at the moment.

Terminology

An argument is a value that a user passes to a variable to control its behavior. A variable receives an argument as a parameter.

Support multiple parameters

Make a variable able to define parameters like this:

protected readonly parameters: IParameters = {
    parameter_name1: {
        type: "string",
        required: true,
    },
    parameter_name2: {
        type: "integer",
        required: false,
    },
    parameter_name3: {
        options: ["static", "value", "options"],
        required: false,
    },
};

protected arguments: {
    parameter_name1: string,
    parameter_name2: number,
    parameter_name3: string,
};

parameter_name1, parameter_name2 and parameter_name3 are internal names for the parameters that are not exposed to users.

A user would write multiple arguments like this: {{variable:argument text:5:static}}, so : works as a separator between arguments. Note that argument text is a single argument, the space is just a normal character.

parameter_name3 is a parameter that can only take predefined values, so the value must be one of: static, value or options.

Support optional parameters

Parameters can be defined optional by setting required to false. Optional parameters can be located after or before mandatory parameters, maybe even in between (but this is untested!).

[Taitava]

Done.

[Taitava]

For some reason this issue was not added into a milestone even though the issue is done already. I added it to 0.6.0, which is a version where this was released in.