Refactor and improve

[redneck-f25]

Here are some more changes.

Hope you like it. Let me know, if you want me to change anything.

There is an issue with the reset button, if the review area has resized. I haven't found a solution yet.

Preview:

• https://redneck-f25.github.io/GraphvizOnline/?presentation=editable,hide-options,show-download&url=https://gist.githubusercontent.com/redneck-f25/10acebf26550cc22aa1d66de88bb1324/raw/example.gv
• https://dreampuf.github.io/GraphvizOnline/?presentation=editable,hide-options,show-download&url=https://gist.githubusercontent.com/redneck-f25/10acebf26550cc22aa1d66de88bb1324/raw/example.gv

Commits in this PR:

• b3ee14f Print caught errors to devtools console
• c0d32f5 Render graph immediately if editor is changed programmatically
  • e.g. when an URL is given in the parameter list
• 6a2298f Refactor collapsible editor and draggable split
  • reduce code for changing the style attribute
  • refactor event handling around splitter
  • add dblclick handler to split to 50%, (as VS Code does)
  • improve resize experience while dragging the splitter and resizing the window
• ec8150b Prevent flickering when dragging the splitter
  • if the coursor leaves the splitter while dragging towards the editor, the cursor changes to 'text' or 'default' until the splitter has reached the new position and is under the cursor
• 2ec405d Add options for presentation mode
  • see README.md
• ca6ea4f Use flexbox to let renderer compute svg position
  • document.getElementById('review').offsetTop === 42 from CSS
  • document.getElementById('options').offsetHeight === 48 from font-size, line-height, padding and whatever
• 757e1a9 2970553 Maintain center point when resizing SVG view
  • when panning and zooming a large graph into view, it is annoying if it's reset to initial size when the editor or window is resized or rotated
• 6585dfa 7e34a06 Add link to GitHub repo to option bar
  • adjust repo url to hostname
• 77edde0 defd456 Render editor gutter with stable width
  • if a large file is loaded into the editor and line number 100 comes into view while scrolling down, the gutter widens and then narrows again when scrolling back up
• 404ca0c 05e88a5 Handle touch events with svg-pan-zoom
  • for mobile devices and touch screens

[redneck-f25]

Found a solution for the mentioned issue. I'll fix this.

[dreampuf]

Thanks! It's great!