Problem: wast filetype should be replaced by wat filetype
Solution: start using the official wat filetype name
runtime: rename `wast` filetype to `wat` (Wasm text format)
The problem is the name of the current filetype wast. When the plugin
was initially created, the file extension for Wasm text format was not
fixed and .wast was more popular.
However, recently .wat became the official file extension for
WebAssembly text (WAT) format and .wast is now a file extension for the
unofficial WAST format, which is a superset of .wat for the convenience
to describe the Wasm specification conformance tests.
https://webassembly.js.org/docs/contrib-wat-vs-wast.html
However for now, let's keep using the `wat` filetype even for the .wast
extension, so that we at least do not lose the filetype settings and
syntax highlighting. This can be adjusted later, if it turns out to have
a separate need for.
closes: vim/vim#13533bc8f79d36a
Co-authored-by: rhysd <lin90162@yahoo.co.jp>
