feat: add grid option enableHtmlRendering to use pure HTML not string

[ghiscoding]

• prior to this PR, SlickGrid only used html string that are then passed to innerHTML but that is not CSP (Content Security Policy) friendly, what could be nice is to provide an HTMLElement directly as Formatter and other areas of the code.
• the goal is to eventually provide the option to the user to remove all usage of innerHTML within SlickGrid by using this new enableHtmlRendering grid option which would fix CSP unsafe issues.
• this PR is NOT complete, at this point it only adds HTMLElement option to column names and Formatters (user can still pass html string, so it won't be a breaking change) but there are still some more usage of innerHTML elsewhere in the code.

subject covered by this PR

• Formatters using pure HTMLElement
• column name using pure HTMLElement

subject NOT covered yet by this PR

• SlickGrid row caching uses innerHTML inside methods like appendCellHtml and appendRowHtml
• DataView uses dynamic new Function to cache certain rows, but CSP is not happy with it unless we use unsafe-eval which is very loose.
  • a possible hack approach would be to use a custom nonce as described in this SO
• both of these are now covered by PR fix: add CSP safe option for DataView filtering and adjusting inline css for CSP #908

Example

prior to this PR, a Formatter would always return a string, even for HTML, like below

checkmarkFormatter(row, cell, val) {
  return `<span class="sgi sgi-check">${val}</span>`;
}

but now with this PR, we can now use pure HTML Element directly in Formatters dropping the need for innerHTML internally

checkmarkFormatter(row, cell, val) {
  const elm = document.createElement('span');
  elm.className = 'sgi sgi-check';
  elm.textContent = val;
  return elm;
}

[JesperJakobsenCIM]

I have done a few changes in these files its simply adding a space between top: and the value and added ; at the end since this is what the default handling comes with

[ghiscoding]

yeah I saw that, the test will probably fail after merging your code into my branch, so I can review them afterward. Thanks for the info