Support tag filter

[zhiyuanliang-ms]

Usage

const config = await load(connectionString, {
    selectors: [
        { tagFilters: ["tag1=", "tag2=someValue] }
    ],
    featureFlagOptions: {
        enabled: true,
        selectors: [
            { tagFilters: ["tag1=", "tag2=someValue] }
        ]
    }
});

[RichardChen820]

Is this check robust? \n is not allowed in tag?

[zhiyuanliang-ms]

I followed .NET provider's implementation: https://github.com/Azure/AppConfiguration-DotnetProvider/pull/637/files#diff-5f9d810c153f73ab4382bfddf40b76b7c30bba39beae6e74557bc078115f3f95

I checked out backend code, we don't forbid \n but the portal will not allow you to enter \n when creating a tag.