Manually update README.md

[jlaehne]

Manually fix the extension list for the time that the script is not running (kikuchipy not being v2.0 compatible).

Avoid confusion as raised in hyperspy/hyperspy#3427

[hakonanes]

Sounds good. Working on 2.0 compatibility.

[ericpre]

The file https://github.com/hyperspy/hyperspy-extensions-list/blob/main/extension_list.txt needs to be updated (remove kikuchipy temporarily) and then run the script as per instructions in https://github.com/hyperspy/hyperspy-extensions-list/blob/main/doc/how_to_add_extension.md#running-the-make_readmepy-script-manually, ans that will update the README.md file.

[jlaehne]

Running the script results in the following error. It seems that print_known_signal_types() only prints the information and does not return anything ... was there some change?

    table_html = hs.print_known_signal_types()._repr_html_()
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute '_repr_html_'

[jlaehne]

Replaced by #62