refactor(nvim): move "table" snippet into `all` filetypes category
refactor(nvim): move "table" snippet into `all` filetypes category

Seeing as I write Markdown-ish commit messages and sometimes what to put
tables in them, move the `table` snippet up into `all` from `markdown`.
In general it's a useful rendering of tables for any plain-text-ish kind
of situation, so seems a reasonable place for it.

Example:

    | First Header  | Second Header |
    | ------------- | ------------- |
    | Content Cell  | Content Cell  |
    | Content Cell  | Content Cell  |

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent