Browser console warning: The main 'lit-element' module entrypoint is deprecated

[RedNo7]

Checklist:

• I updated to the latest version available
• I cleared the cache of my browser

Release with the issue:
1.3.6

Last working release (if known):
n/a

Browser and Operating System:
Safari 16.6
MacOS 13.6
...same warning in Firefox.

Description of problem:
The browser (Safari, Firefox) console shows the following warning:

The main 'lit-element' module entrypoint is deprecated. Please update your imports to use the 'lit' package: 'lit' and 'lit/decorators.ts' or import from 'lit-element/lit-element.ts'. See https://lit.dev/msg/deprecated-import-path for more information.

Javascript errors shown in the web inspector (if applicable):

Additional information:

[ildar170975]

Duplicate #91