CSS and JS of custom content module are typically included via
<tml:include designdb="@cmm" ref="htmlhead-includes"/>
If your site is based on basic-website-kit exactly this include is (behind the scene) part of the @base plugin.
This now can be done by adding an option "css-version" and/or "js-version" to the include.
If your site is BWK-based this can be done in TML "layout:head":
You need to change the value every time you changed your module-css/js.