Fix value stored in element options for indexable option

[stockiNail]

The PR #801 introduced indexable options (font and color).

The current options resolution is checking if the options is indexable and if true, it stores the value of the options.

chartjs-plugin-annotation/src/elements.js

Line 134 in bc38d6b

result[prop] = isObject(optDefs) && !isIndexable(prop) ? resolveObj(value, optDefs) : value;

In this way, it stores a Proxy object (or an array of Proxy) in element options, something that probably you don't want.

This PR is storing "plain" objects as element.options.

[stockiNail]

Thank youu @kurkle