Add a new bidder adapter ：mediagoBidderAdapter

[SylviaF]

Type of change

• [] Bugfix
• [] Feature
• New bidder adapter
• [] Code style update (formatting, local variables)
• [] Refactoring (no functional changes, no api changes)
• [] Build related changes
• [] CI related changes
• [] Does this change affect user-facing APIs or examples documented on http://prebid.org?
• [] Other

Description of change

Add a new bidder adapter called mediagoBidderAdapter.
Our official website is https://www.mediago.io/

• test parameters for validating bids

{
	bidder: 'mediago',
	params: {
		token: '85a6b01e41ac36d49744fad726e3655d' // required, send email to [email protected] to get the corresponding token
	}
}

Be sure to test the integration with your adserver using the Hello World sample page.

• contact email of the adapter’s maintainer（[email protected]）
• official adapter submission

For any changes that affect user-facing APIs or example code documented on http://prebid.org, please provide:

• A link to a PR on the docs repo at https://github.com/prebid/prebid.github.io/

Other information

[lgtm-com]

This pull request introduces 50 alerts when merging 5aecdb8 into db02d8a - view on LGTM.com

new alerts:

• 50 for Useless regular-expression character escape

[lgtm-com]

This pull request introduces 50 alerts when merging dc364b1 into db02d8a - view on LGTM.com

new alerts:

• 50 for Useless regular-expression character escape

[lgtm-com]

This pull request introduces 50 alerts when merging 5c9fb22 into 97713dd - view on LGTM.com

new alerts:

• 50 for Useless regular-expression character escape

[bretg]

Docs PR prebid/prebid.github.io#2234

[GLStephen]

LGTM - thanks for providing a 100% fill bidder example

[patmmccann]

Hi @SylviaF

You may have noticed all the regular expression issues flagged in the lgtm alert
#5614 (comment)

Would you consider fixing?

Thanks!