fix(gitignore): anchor "coverage/" rule to repo root (#127)
The unanchored "coverage/" rule (intended to ignore the test-output
directory at repo root) silently matches any "coverage/" directory in
the tree. This bit a real PR: src/coverage/ was added but never made
it into the commit because git add silently dropped the files. The
PR shipped with the test importing a module that didn't exist.
Anchor the rule to "/coverage/" so it only ignores root-level test
output, allowing src/coverage/, packages/*/coverage/, etc. to be
committed normally.
andreinknv