web3-eth-miner documentation

[princesinha19]

Description

Documentation added for web3-eth-miner. All methods of miner listed in https://github.com/ethereum/go-ethereum/wiki/Management-APIs#miner.

Releated to: #2660

Type of change

• Documentation

Checklist:

• I have selected the correct base branch.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no warnings.
• I have updated or added types for all modules I've changed
• Any dependent changes have been merged and published in downstream modules.
• I ran npm run test in the root folder with success and extended the tests if necessary.
• I ran npm run build in the root folder and tested it in the browser and with node.
• I ran npm run dtslint in the root folder and tested that all my types are correct
• I have tested my code on an ethereum test network.

[coveralls]

Coverage remained the same at 95.491% when pulling 5afd630 on princesinha19:miner-documentation into bb891b2 on ethereum:1.0.

[princesinha19]

@nivida I changed the Miner documentation. I think you should review the latest commit. I changed Txpool and Admin documentation too.