docs: rename repository from oil.nvim to canola.nvim

Problem: the fork shared the same name as upstream, making it difficult
to distinguish and discover independently.

Solution: rename the repository to canola.nvim — a type of oil, making
the lineage obvious while establishing a distinct identity. Update all
references in the README, rockspec, and issue templates.

oil.nvim-scm-1.rockspec

@@ -1,30 +0,0 @@
-rockspec_format = '3.0'
-package = 'oil.nvim'
-version = 'scm-1'
-
-source = {
-  url = 'git+https://github.com/barrettruth/oil.nvim.git',
-}
-
-description = {
-  summary = 'Neovim file explorer: edit your filesystem like a buffer',
-  homepage = 'https://github.com/barrettruth/oil.nvim',
-  license = 'MIT',
-}
-
-dependencies = {
-  'lua >= 5.1',
-}
-
-test_dependencies = {
-  'nlua',
-  'busted >= 2.1.1',
-}
-
-test = {
-  type = 'busted',
-}
-
-build = {
-  type = 'builtin',
-}