Immediately use installed Node.js version

[mbwestphal]

Currently, when you run fnm use and the expected version is missing, fnm will ask you whether to install it. If you confirm that, fnm will install the new version but you will have to run fnm use again to actually use it:

$ node -v
v17.9.1
$ echo v17.0.1 > .node-version
$ fnm use
Can't find an installed Node version matching v17.0.1.
Do you want to install it? answer [y/N]: y
Installing Node v17.0.1 (x64)
00:00:04 ██████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████ 21.16 MiB/21.16 MiB (4.72 MiB/s, 0s)
Enabling corepack for Node v17.0.1
$ node -v
v17.9.1
$ fnm use
Using Node v17.0.1
$ node -v
v17.0.1

This is very unexpected.