Add map values

[m0sth8]

• map[string]string
• map[string]int

Something similar to kingpin`s stringMap implementation https://github.com/alecthomas/kingpin/blob/bf17db2c43f59ff3d97a39d1feacef18d75eaf95/values.go#L135

--map=key1:val1 --map=key2:val2

[dolmen]

I have implemented a generic Map Value in my package github.com/dolmen-go/flagx designed to extend flag.

[furdarius]

Can be closed.

[dearchap]

@m0sth8 This feature is already present in sflags correct ? Can I close ?