Better README for Windows PowerShell

[ryul1206]

Is your feature request related to a problem? Please describe.
The current README is not friendly to people.

Describe the solution you'd like

1. Better description to solve PowerShell issues.
2. Provide a download link to the PSmmg folder. (https://minhaskamal.github.io/DownGit/#/home?url=https://github.com/ryul1206/multilingual-markdown/tree/master/PSmmg)

[ryul1206]

In addition to the "Command Not Found" issue, there is another issue that can occur when the python command is not available and only the python3 command exists. This issue mainly arises when the PSmmg.psm from the mmgcli tries to call the python command, which is not available. The error message for this issue looks like:

Program 'python' failed to run: No application is associated with the specified file for this operationAt C:\Program Files\WindowsPowerShell\Modules\PSmmg\PSmmg.psm1:2 char:5
+     python -m mmgcli $args
+     ~~~~~~~~~~~~~~~~~~~~~~.
At C:\Program Files\WindowsPowerShell\Modules\PSmmg\PSmmg.psm1:2 char:5
+     python -m mmgcli $args
+     ~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ResourceUnavailable: (:) [], ApplicationFailedException
    + FullyQualifiedErrorId : NativeCommandFailed

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[ryul1206]

From version 2.0.0, Poetry is used, which means that PSmmg.psm is no longer required. This issue seems to be resolved.