Add issue templates, fixed readme

[elenagaljak-db]

What changes are proposed in this pull request?

Provide the readers and reviewers with the information they need to understand
this PR in a comprehensive manner.

Specifically, try to answer the two following questions:

• WHAT changes are being made in the PR? This should be a summary of the
  major changes to allow the reader to quickly understand the PR without having
  to look at the code.
• WHY are these changes needed? This should provide the context that the
  reader might be missing. For example, were there any decisions behind the
  change that are not reflected in the code itself?

The “why part” is the most important of the two as it usually cannot be
inferred from the code itself. A well-written PR description will help future
developers (including your future self) to know how to interact and update your
code.

How is this tested?

Describe any tests you have done; especially if test tests are not part of
the unit tests (e.g. local tests).

ALWAYS ANSWER THIS QUESTION: Answer with "N/A" if tests are not applicable
to your PR (e.g. if the PR only modifies comments). Do not be afraid of
answering "Not tested" if the PR has not been tested. Being clear about what
has been done and not done provides important context to the reviewers.

[teodordelibasic-db]

BTW I think you should remove all of the PR description template except the headings, so it should look like this:

## What changes are proposed in this pull request?

<YOUR TEXT>

## How is this tested?

<YOUR TEXT>