Add Mermaid copy button, avoid unnecessary tooltip hide (#22225)

- Add Copy button to mermaid diagrams which copies their source.
- Set tippy to not hide on click and avoid tooltip re-creation for
temporary tooltips. This avoids hide and show when copying repo url.
Popovers still hide the tooltip as usual.


<img width="815" alt="Screenshot 2022-12-23 at 14 02 32"
src="https://user-images.githubusercontent.com/115237/209341696-98e30953-f246-46d9-9157-2ececfd791c9.png">

Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: KN4CK3R <admin@oldschoolhack.me>

web_src/less/markup/codecopy.less

@@ -1,4 +1,5 @@
-.markup .code-block {
+.markup .code-block,
+.markup .mermaid-block {
   position: relative;
 }
 
@@ -26,7 +27,8 @@
   background: var(--color-secondary-dark-1) !important;
 }
 
-.markup .code-block:hover .code-copy {
+.markup .code-block:hover .code-copy,
+.markup .mermaid-block:hover .code-copy {
   visibility: visible;
   animation: fadein .2s both;
 }