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.

canola.nvim-scm-1.rockspec

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