Update Video Templates To Match Website Theme

The templates shown in the beginning of each video in the Learning Path used to match the general theme of the InnerSource Commons website. The website got a fresh new look at some point, but, the video templates have not.

The website's new theme uses teal (#0CA7A7) as the main action color and PT Sans as the font. The logo has also been refreshed to have a smaller outer border.

At a bare minimum, it would be great if the existing templates could use the new logo, colors, and fonts. If we're feeling slightly more adventurous, we could go for a look that matches overlays found in other areas of the website (see the Announcements section for an example). And if we're feeling really ambitious we could design something totally new and unique and use that.

It's totally up to whoever takes up this issue how they want to go about solving it, so long as they collaborate with the group as they go.

Keep in mind that any template we use will also need to be applied to the static images we use for workbooks (or some variation of it at least).

@lenucksi pointed out the original templates, created by @RJPlog, are located here:
https://github.com/InnerSourceCommons/InnerSourceLearningPath/blob/main/assets/thumbnails/thumbnail_template.odg

Start with assets/thumbnails/thumbnail_template.odg and compare it with the current website theme, especially the Announcements section. Review the existing video templates and static workbook images, then define a consistent treatment using the refreshed logo, teal color, and PT Sans. Done means the selected template style is applied to both videos and workbook imagery and has been reviewed with the group.