feat: support .mjs extension resolution (#2283)

Removed `extmap` and added .mjs entry in `map_file_extension`.
The assert in the compiler does not need to be updated, since it is
resolving from the compiled cache instead of elsewhere (notice the .map
is asserted next to it)

1 files changed, 1 insertions, 0 deletions

diff --git a/tests/subdir/mod5.mjs b/tests/subdir/mod5.mjs
new file mode 100644
index 000000000..f21d8862b
--- /dev/null
+++ b/tests/subdir/mod5.mjs
@@ -0,0 +1 @@
+export const isMod5 = true;