add MARKETS_API_INFO env var

[nonsense]

When lotus-miner CLI is trying to connect to a remote lotus-miner (split between multiple machines, or not), it doesn't have any local repos, but needs to know the location of the markets-api, so the user should explicitly specify it in MARKETS_API_INFO.

This is an edge case, when the machine on which lotus-miner CLI client command is run has no repos, but given the fallback repo locations, it still tries to read ~/.lotusminer for the API endpoint in case MARKETS_API_INFO is not specified.

[filecorgi]

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docs/mine/lotus/miner-setup.md:

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  ...configure a Lotus miner for production. WARNING Mining will only work if you...
                                             ^^^^^^^
  

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  ...installed. Make sure your Lotus Node is running as the miner will communicat...
                                             ^^^^^^^
  

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  ...ng separate owner and worker addresses: Next make sure to send some funds to...
                                             ^^^^
  

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  ...you are using the systemd service file: WARNING Do not proceed from here unt...
                                             ^^^^^^^
  

docs/mine/lotus/seal-workers.md:

• The verb ‘set up’ is spelled as two words. The noun ‘setup’ is spelled as one.

  ...r processes. This guide explains how to setup one or several Lotus Workers. ...
                                             ^^^^^
  

• Use “an” instead of ‘a’ if the following word starts with a vowel sound, e.g. ‘an article’, ‘an hour’.

  ... it. That means that a single worker on a 8-core CPU with a single GPU will ...
                                             ^
  

• Did you mean “tables”?

  ...e system can use a GPU. # Task resource table The default resource table liv...
                                             ^^^^^
  

• If a new sentence starts here, add a space and start with an uppercase letter.

  ...fault resource table lives in resources.go  (opens new window) and can be ed...
                                             ^^
  

• ‘takes into account’ might be wordy. Consider a shorter alternative.

  ...cheduler decides which tasks to run, it takes into account the priority of r...
                                             ^^^^^^^^^^^^^^^^^^
  

• If this is a compound adjective that modifies the following noun, use a hyphen.

  ...priority. When comparing task priority: High priority tasks are considered f...
                                             ^^^^^^^^^^^^^
  

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  ...to connect to the Lotus Miner. For more info check the API docs. Write down ...
                                             ^^^^
  

• Only proper nouns start with an uppercase character (there are exceptions for headlines).

  ...g Lotus workers # Environment variables Ensure that workers have access to t...
                                             ^^^^^^
  

• Unpaired symbol: ‘)’ seems to be missing

  ...milar to those used by the Miner daemon (explained in the setup guide: TIP W...
                                             ^
  

• Did you mean “co-locate a miner”?

  ...ers and Lotus Workers. Note that if you co-locate miner and worker(s), you d...
                                             ^^^^^^^^^^^^^^^
  

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  ... one Lotus Worker per machine should be running since lotus-worker will try ...
                                             ^^^^^^^