Add support to customize ethers.js log level

[acuarica]

While editing a document in ethers mode, usually the intermediate edits lead to errors that are logged in the console.
Since there can be many, this can pollute the console error messages.

Add a configuration property to allow the user to define the log level[1] of ethers.js.
The levels defined by ethers.js are[2]

• DEBUG Log all output, including debugging information.
• INFO Only log output for informational, warnings and errors.
• WARNING Only log output for warnings and errors.
• ERROR Only log output for errors.
• OFF Do not output any logs.

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[1] https://docs.ethers.io/v5/api/utils/logger/#Logger-setLogLevel
[2] https://docs.ethers.io/v5/api/utils/logger/#Logger-levels