Add documentation issue template. (#1425)

* Create documentation.md

.github/ISSUE_TEMPLATE/documentation.md

@@ -0,0 +1,51 @@
+---
+name: Documentation
+about: Report an issue relating to this project's documetation.
+title: ''
+labels: documentation
+assignees: ''
+
+---
+
+<!-- Please only include one item in each issue! -->
+
+This is about:
+- [ ] A typo 
+- [ ] Innaccurate/misleading documentation (e.g. technically incorrect advice)
+- [ ] Undocumented code
+- [ ] Outdated documentation
+- [ ] Other
+
+**Problem**
+<!-- PLEASE INCLUDE A WAY TO LOCATE WHERE THE ISSUE IS, e.g.
+ - A Github link to the text
+ - The filename and line number
+ - An excerpt from the docs that someone could use text search to locate
+-->
+<!-- What's wrong? -->
+
+<!-- EXAMPLES FOR TYPOS: -->
+<!-- e.g. There's a typo in the documentation about the `html!` macro. 
+It's in the word on line 14 column 5 in file "..." Here's a link to the text on Github "https://github.com/..." -->
+<!-- e.g. There's a typo in this sentence "..." on the webpage "https://yew.rs/..." -->
+
+<!-- EXAMPLES FOR MISLEADING DOCS -->
+<!-- e.g. The sentence "..." implies "..." but this is misleading because it might cause someone 
+to think "..." which is wrong. -->
+
+<!-- EXAMPLES FOR MISSING DOCS -->
+<!-- e.g. There's no API documentation for the console service. -->
+<!-- e.g. There's no documentation on yew.rs for the console service. -->
+
+<!-- EXAMPLES FOR OUTDATED DOCS -->
+<!-- e.g. The documentation about the `html!` macro was written for a previous version of Yew and should be updated. -->
+
+**Details about the solution you'd like** _(Optional)_
+
+**Additional context** _(Optional)_
+<!-- e.g. examples of similar documentation which is of high quality -->
+
+**Questionaire** _(Optional)_
+- [ ] I'd like to write this documentation
+- [ ] I'd like to write this documentation but I'm not sure what's needed
+- [ ] I don't have time to add this right now, but maybe later