[Suggestion] `lib.convar`

[D4isDAVID]

Is your feature request related to a problem? Please describe.
Nowadays, convars in FiveM are mostly calculated once, and never again after resources are already started.
Meaning when someone wants to change a resource's configuration using convars, most resources require a restart as the convars are only calculated when initially started.

A solution is available, called AddConvarChangeListener. However, it requires additional boilerplate.
Another issue is tables/objects/arrays, which are not natively supported by convar natives.

Describe the solution you'd like
My proposal is a new lib.convar API that allows developers to quickly define their convars, with a change listener added under the hood. In addition, a custom parser can be used to return values of various types.

Example proposal:

-- typical string convar
local strConvar = lib.convar.string('myResource:myStringConvar', 'default value')

print(strConvar.name) -- myResource:myStringConvar
print(strConvar.value) -- default value
print(strConvar.defined) -- false

ExecuteCommand('set myResource:myStringConvar "some custom value"')

print(strConvar.name) -- myResource:myStringConvar
print(strConvar.value) -- some custom value
print(strConvar.defined) -- true

-- other common types
local intConvar = lib.convar.int('myResource:myIntConvar', 123)
local floatConvar = lib.convar.float('myResource:myFloatConvar', 0.2)
local boolConvar = lib.convar.bool('myResource:myBoolConvar', true)

-- custom types
local tableConvar = lib.convar('myResource:myTableConvar', {
    foo = 'bar',
}, function(value)
    local tble = json.decode(value)

    if type(tble) ~= 'table' then
        error('bad type!')
    end

    return tble
end)

print(strConvar.value.foo) -- bar

ExecuteCommand('set myResource:myTableConvar "some custom value"') -- error parsing convar 'myResource:myTableConvar': bad type!

Additional context
I'm willing to implement this myself, but opening an issue beforehand for some feedback.

Here are a few links related to convars:

• Convars - Cfx.re Docs
• ADD_CONVAR_CHANGE_LISTENER