Fix failing HTML checks
We now have a Continuous Integration pipeline, as per #122. However, there are some errors that need to be fixed for valid HTML and accessibility:
line 34 column 33 - Warning: missing </button> before <div>
line 35 column 68 - Warning: inserting implicit <button>
line 36 column 33 - Warning: discarding unexpected </button>
line 201 column 53 - Warning: unescaped & or unknown entity "&I"
line 95 column 149 - Warning: <img> lacks "alt" attribute
line 34 column 33 - Warning: trimming empty <button>
line 35 column 68 - Warning: trimming empty <span>
line 35 column 81 - Warning: trimming empty <span>
line 35 column 94 - Warning: trimming empty <span>
line 35 column 107 - Warning: trimming empty <span>
line 35 column 68 - Warning: trimming empty <button>
line 343 column 41 - Warning: <a> proprietary attribute "dnt"
Info: Document content looks like HTML5
Tidy found 12 warnings and 0 errors!