Partial implementation fill-tags plus update tests
Implement {% fill %} tags. Next: update tests.
Bring back support for {%slot%} blocks for bckwrd-compat and implement ambig. resolution policy
Update tests to use fill blocks. Add extra checks that raise errors
Add new tests for fill-slot nesting
Update README. Editing still required
remove unused var ctxt after flake8 complaint
fix flake8 warning about slotless f-string
[pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
Add new slot aliases in fill context. Clean up rendering logic in Component. Update docs.
fix flake8, isort, black errors
Refactor duplicated name validation
Add if_filled tag + elif_filled...else_filled...endif_filled for cond. slots
Fix mistake in do_if_filled() docstring
Upload templates for tests! D'oh
Incorporate PR feedback
Drop Literal type hint; Use isort off-on instead of skip in tests
Treat all fill,slot,if_filled,component names as variables
Reset sampleproject components
Add test for variable filled name
Update examples in docs
