README: fix "Github ursername" typo (#130)

## Summary

- Fix two instances of "Github ursername" in `README.md` and
`examples/README.jl` (correcting the misspelling and the GitHub
canonical capitalization).

## Test plan

- [x] `itpkgfmt` clean.
- [x] Pre-commit hooks pass.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: mtfishman

Project.toml

@@ -1,6 +1,6 @@
 name = "ITensorPkgSkeleton"
 uuid = "3d388ab1-018a-49f4-ae50-18094d5f71ea"
-version = "0.3.52"
+version = "0.3.53"
 authors = ["ITensor developers <support@itensor.org> and contributors"]
 
 [workspace]

README.md

@@ -31,7 +31,7 @@ or:
 ```julia
 julia> Pkg.Registry.add(url = "git@github.com:ITensor/ITensorRegistry.git")
 ```
-if you want to use SSH credentials, which can make it so you don't have to enter your Github ursername and password when registering packages.
+if you want to use SSH credentials, which can make it so you don't have to enter your GitHub username and password when registering packages.
 
 Then, the package can be added as usual through the package manager:
 

examples/README.jl

@@ -31,7 +31,7 @@ julia> Pkg.Registry.add(url = "https://github.com/ITensor/ITensorRegistry")
 julia> Pkg.Registry.add(url = "git@github.com:ITensor/ITensorRegistry.git")
 ```
 =#
-# if you want to use SSH credentials, which can make it so you don't have to enter your Github ursername and password when registering packages.
+# if you want to use SSH credentials, which can make it so you don't have to enter your GitHub username and password when registering packages.
 
 # Then, the package can be added as usual through the package manager: