Fix breaking change: missing PlatformIO integration of new dependency package ghostl

[maxgerhardt]

The library.json references the dok-net/ghostl library via a PIO Registry version string, but no such library exists.

Making it just reference the stable 1.0.1 version from github makes it work.

Alternatively register the package (I've actually done that as maxgerhardt/ghostl @ ^1.0.1, the PIO Registry hopefully picks it up soon) and reference it correctly in the library.json. But referencing non-existing packages makes PIO go kaboom.

Test install and proof:

>pio pkg install -g -l https://github.com/maxgerhardt/espsoftwareserial.git
Library Manager: Installing git+https://github.com/maxgerhardt/espsoftwareserial.git
git version 2.38.1.windows.1
Cloning into 'C:\Users\Max\.platformio\.cache\tmp\pkg-installing-zn187w8b'...
remote: Enumerating objects: 24, done.
remote: Counting objects: 100% (24/24), done.
remote: Compressing objects: 100% (18/18), done.
remote: Total 24 (delta 1), reused 10 (delta 0), pack-reused 0
Receiving objects: 100% (24/24), 32.20 KiB | 6.44 MiB/s, done.
Resolving deltas: 100% (1/1), done.
Library Manager: [email protected]+sha.6d91487 has been installed!
Library Manager: Resolving dependencies...
Library Manager: Installing https://codeload.github.com/dok-net/ghostl/zip/refs/tags/1.0.1
Downloading...
Unpacking  [####################################]  100%
Library Manager: [email protected] has been installed!

Fixes #307

[maxgerhardt]

FYI the maxgerhardt/ghostl library has been published in the registry per https://registry.platformio.org/libraries/maxgerhardt/ghostl/installation, but I still think it's better to either put a link to a repo the real owner controls or the owner has control over the PIO registry package.

[dok-net]

I have published ghostl under my account now...