ox-html.el: Fix or add docstring

ox-html.el: Fix or add docstring

* ox-html.el (org-html-text-markup-alist)
(org-html-pretty-output, org-html-link-org-files-as-html)
(org-html-postamble, org-html-preamble)
(org-html-format-inline-image, org-html-splice-attributes)
(org-export-splice-style, org-html-htmlize-region-for-paste)
(org-html-fix-class-name)
(org-html-format-footnote-reference)
(org-html-format-footnotes-section)
(org-html-footnote-section, org-html--anchor)
(org-html--todo, org-html--tags, org-html-format-headline)
(org-html-toc, org-html-format-section, org-html-checkbox)
(org-html-format-list-item, org-html-format-latex)
(org-html-encode-plain-text)
(org-html-table-first-row-data-cells)
(org-html-table--table.el-table, org-html-final-function): Fix
or add docstring.