zh-tw: Partially translated files

[queengooborg]

During a Pretter run, I noticed a number of files in the Traditional Chinese translations that are not fully translated. These files will probably needed to be resynchronized with upstream, or deleted. These include:

### Learn
- [ ] Learn/HTML/Introduction_to_HTML/HTML_text_fundamentals
- [ ] Learn/server-side/django/django_assessment_blog
- [ ] Learn/server-side/django/forms
- [ ] Learn/server-side/express_nodejs/development_environment
- [ ] Learn/tools_and_testing/cross_browser_testing/automated_testing

### Web
- [ ] Web/API/setInterval
- [ ] Web/CSS/@font-face
- [ ] Web/CSS/_colon_target
- [ ] Web/CSS/_doublecolon_first-letter
- [ ] Web/CSS/background-attachment
- [ ] Web/CSS/box-sizing
- [ ] Web/CSS/clip
- [ ] Web/CSS/CSS_colors
- [ ] Web/CSS/CSS_colors/applying_color
- [ ] Web/CSS/CSS_flexible_box_layout/basic_concepts_of_flexbox
- [ ] Web/CSS/CSS_grid_layout/basic_concepts_of_grid_layout
- [ ] Web/CSS/CSS_selectors/using_the__colon_target_pseudo-class_in_selectors
- [ ] Web/CSS/cursor
- [ ] Web/CSS/gradient/radial-gradient
- [ ] Web/CSS/grid-template
- [ ] Web/CSS/grid-template-columns
- [ ] Web/CSS/inheritance
- [ ] Web/CSS/object-fit
- [ ] Web/CSS/transform-function
- [ ] Web/CSS/white-space
- [ ] Web/CSS/width
- [ ] Web/events/event_handlers
- [ ] Web/html/block-level_elements
- [ ] Web/html/element
- [x] Web/html/element/a  #18791
- [x] Web/html/element/button #18855
- [x] Web/html/element/form #19125
- [ ] Web/html/element/input
- [ ] Web/html/element/meter
- [ ] Web/html/element/optgroup
- [ ] Web/html/element/script
- [ ] Web/html/element/summary
- [ ] Web/html/element/table
- [ ] Web/html/global_attributes
- [x] Web/http/basics_of_http/data_urls #20837
- [ ] Web/http/basics_of_http/mime_types
- [x] Web/http/headers/accept #19855
- [x] Web/http/headers/content-type #20682
- [x] Web/http/headers/server #20681
- [ ] Web/http/headers/strict-transport-security
- [x] Web/http/headers/user-agent #20677
- [ ] Web/JavaScript/Reference/Errors/Not_defined
- [ ] Web/JavaScript/Reference/Global_Objects/Array/forEach
- [ ] Web/Media/Formats/Containers
- [ ] Web/opensearch
- [ ] Web/svg/tutorial/paths
- [ ] Web/tutorials

[SphinxKnight]

Thanks a lot for this @queengooborg <3