docs: use relative URLs instead of site.baseurl

BS3 commits: f59573db0d4dd6f7f1e3b2c62058298de771a257
fix 12314

BS3 commits: 4a36ecaac64dea84be85b4876fc3c8d20d87f8e8
Corrected tag for Alert JS animation example from <a> to <button>

BS3 commits: 4380ca434885f33072885e639a2d29cc203771bd
fix 12311

BS3 commits: 4552bcf66fcaa0a6b40888efd99769edd91aa3bf