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

从 assets/thumbnails/thumbnail_template.odg 开始，并将其与当前网站主题进行比较，尤其是 Announcements 部分。检查现有的视频模板和静态 workbook 图片，然后使用更新后的 logo、teal 颜色和 PT Sans 定义一致的设计处理方式。选定的模板样式应用于视频和 workbook 图片，并已与团队一起审阅后，即视为完成。