Add --world option and support test somewhere with predefined location

[r3inbowari]

When using the new api, we can easily change the current location to get a different server list. implement #2 Use map to pre-mark each location

usage: Select the best server under the current label for testing ~~.\speedtest-go.exe --world=beijing~~ .\speedtest-go.exe --city=tokyo

List servers under the current label ~~.\speedtest-go.exe --world=paris -l~~ .\speedtest-go.exe --city=tokyo -l

[r3inbowari]

also, we can use like this to select a precise and valid location: ~~.\speedtest-go.exe --world 35.6778832,139.7803794~~ ~~.\speedtest-go.exe --world 35.6778832,139.7803794 -l~~ .\speedtest-go.exe --location 35.6778832,139.7803794 .\speedtest-go.exe --location 35.6778832,139.7803794 -l

And all input format errors will be caught and skipped: ~~ .\speedtest-go.exe --world 35.6778832,189~~ .\speedtest-go.exe --location 35.6778832,189 Warning: skipping command line arguments: --location. err: invalid input. got: 189, expected between -180 and 180

[showwin]

@r3inbowari Thank you for implementing my rough idea 😂 I thought about --world option that runs speedtest to 6 regions all over the world continuously and averages or summarizes the data to show the result. This option would be useful for those who care about bandwidth all over the world.

Though your idea is also great. How about using --location 35.6778832,139.7803794 instead of --world? I think --location name describes its behavior better. and if --location can receive both <Lat>,<Lon> like 35.6778832,139.7803794 and city names, I think the interface is a bit weird so I recommend to use --city tokyo for city names if you want.

[r3inbowari]

Yes, I totally agree.

[showwin]

@r3inbowari Thank you again🌟 And sorry for late review 🙏🙏🙏