Update readme with new utility functions for current_exe and temp_dir #92

Job	Run time
Verify code formatting (windows-latest)	46s
Run examples using Rust stable (ubuntu-latest)	15s
Test Rust stable (windows-latest, x86_64-pc-windows-msvc --all-features)	1m 10s
Verify code formatting (ubuntu-latest)	11s
Lint with clippy (windows-latest, --all-features)	44s
Test Rust stable (windows-latest, x86_64-pc-windows-msvc --no-default-features)	1m 18s
Lint with clippy (windows-latest, --no-default-features)	34s
Test Rust stable (macos-latest, --all-features)	33s
Lint with clippy (ubuntu-latest, --all-features)	42s
Test Rust stable (macos-latest, --no-default-features)	57s
Lint with clippy (ubuntu-latest, --no-default-features)	13s
Test Rust stable (ubuntu-latest, --all-features)	34s
Test Rust stable (ubuntu-latest, --no-default-features)	29s
Test Rust stable (ubuntu-latest, wasm32-unknown-unknown --all-features)	14s
Test Rust stable (ubuntu-latest, wasm32-unknown-unknown --no-default-features)	13s
Test Rust 1.58.1 (ubuntu-latest, --all-features)	41s
Test Rust 1.58.1 (ubuntu-latest, --no-default-features)	33s
	10m 7s

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