Add issue templates (#391)

Co-authored-by: Laurence Kedward <laurence.kedward@bristol.ac.uk>

Author: awvwgk

.github/ISSUE_TEMPLATE/01_bug.md

@@ -0,0 +1,25 @@
+---
+name: Bug report
+about: Something is not working
+labels: bug
+---
+
+<!-- Thanks for taking the time to report a bug -->
+<!-- Fill in all entries in this template to make the process as efficient as possible for everyone involved -->
+
+**Describe the issue**
+<!-- Please include steps to reproduce your issue, provide example code snippets if possible -->
+
+**Expected behaviour**
+<!-- What did you expect to happen instead -->
+
+**Technical Details**
+<!-- Please provide us with some technical details in case we have to reproduce the issue ourselves -->
+*stdlib version*
+<!-- latest version is subject to change, copy the commit hash here (git show-ref HEAD) -->
+
+*Compiler version*
+<!-- e.g. GCC 10.2, Intel Fortran classic 21.1, ... -->
+
+*Platform and Architecture*
+<!-- e.g. Windows 10/x86_64, MacOS/aarch64, ... -->

.github/ISSUE_TEMPLATE/02_proposal.md

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+---
+name: Proposal
+about: An idea for a new feature
+labels: idea
+---
+
+<!-- Thanks for proposing a new feature for stdlib -->
+
+**Description**
+<!-- Please describe the feature, please provide examples -->
+<!-- Use codefences (```) to add literal codeblocks for examples -->
+
+**Prior Art**
+<!-- Are there projects implementing the proposed functionality already -->