Update issue/PR templates, contributing.rst, CI

- Keep documentation in sync with master branch

- Run PyLint and MyPy on Github Actions

- Update Issue templates, enforce usage of issue templates, add links to
  resources in Instaloader Documentation

- Update contributing.rst

.github/workflows/lint.yml

@@ -0,0 +1,30 @@
+name: PyLint and MyPy
+
+on: [push, pull_request]
+
+jobs:
+  lint:
+    name: PyLint and MyPy
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: [3.5, 3.6, 3.7, 3.8]
+    steps:
+      - name: Checkout Instaloader Repository
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0  # needed for building docs
+      - name: Setup Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install Dependencies
+        run: |
+          python -m pip install pipenv==2020.6.2
+          pipenv sync --dev
+      - name: PyLint
+        run: pipenv run pylint instaloader
+      - name: MyPy
+        run: pipenv run mypy -m instaloader
+      - name: Build Documentation
+        run: pipenv run make -C docs html SPHINXOPTS="-W -n"

.github/workflows/stale.yml

@@ -7,6 +7,7 @@ on:
 jobs:
   stale:
 
+    name: Mark stale issues and pull requests
     runs-on: ubuntu-latest
     
     steps:

.github/workflows/windows_exe.yml

@@ -4,6 +4,7 @@ on: [push, pull_request]
 
 jobs:
   build:
+    name: Windows EXE build
     runs-on: windows-latest
     steps:
       - name: Checkout Instaloader repository