(chore) Update issue templates (#2574)

Co-authored-by: Vladimir Jimenez <allejo@me.com>

Author: joshgoebel

.github/ISSUE_TEMPLATE/language-request.md

@@ -0,0 +1,42 @@
+---
+name: Language request
+about: I really wish Highlight.js could highlight ...
+title: PLEASE read the below carefully.
+labels: ''
+assignees: ''
+
+---
+
+First let us say that we'd also love it if Highlight.js could highlight whichever language you're about to request support for!  And there is a chance you can help make that happen! But first...
+
+...PLEASE READ THE FOLLOWING...
+
+    Highlight.js does not have a fundamental plan for implementing new languages
+    - i.e., the core team doesn't usually develop new languages. The core team
+    instead focuses on parser development, bugs, and supporting the existing
+    languages. They also currently does not have time to review, merge and
+    maintain any additional languages (fixing bugs, dealing with issues, etc).
+
+    Instead, the project works by encouraging 3rd party language grammars from
+    contributors willing to help develop and maintain them. We're also happy to
+    host those 3rd party language grammars at the ``highlightjs`` GitHub
+    organization - no matter how obscure or weird. Or you're wlecome to host it
+    yourself - we're still happy to link to it.
+
+    This means that *there's no point in requesting a new language without also
+    providing a 3rd party implementation* (we'll simply close "Please support
+    language Xyz" issues with a link to this explanation). If you'd like to see
+    a particular language available but cannot implement it, the best way to
+    make it happen is to find another developer interested in doing so.
+
+    For more info on actually developing a language see our :doc:`language-guide`,
+    and for information on how to properly package your 3rd party language module
+    see :doc:`language-contribution`.
+
+If you are interested in contributing a 3rd party language grammar you can start with: 
+
+- https://highlightjs.readthedocs.io/en/latest/language-contribution.html
+
+---
+
+You actually don't need to create this issue at all unless you have a specific question about the 3rd party language grammar creation process - which we'd be glad to answer.