Update Rust crate base64 to 0.20.0 (#1683)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [base64](https://github.com/marshallpierce/rust-base64) | dependencies | minor | `0.13.1` -> `0.20.0` |

---

### Release Notes

<details>
<summary>marshallpierce/rust-base64</summary>

### [`v0.20.0`](https://github.com/marshallpierce/rust-base64/blob/HEAD/RELEASE-NOTES.md#&#8203;0200)

[Compare Source](marshallpierce/rust-base64@v0.13.1...v0.20.0)

##### Breaking changes

-   Update MSRV to 1.57.0
-   Decoding can now either ignore padding, require correct padding, or require no padding. The default is to require correct padding.
    -   The `NO_PAD` config now requires that padding be absent when decoding.

#### 0.20.0-alpha.1

##### Breaking changes

-   Extended the `Config` concept into the `Engine` abstraction, allowing the user to pick different encoding / decoding implementations.
    -   What was formerly the only algorithm is now the `FastPortable` engine, so named because it's portable (works on any CPU) and relatively fast.
    -   This opens the door to a portable constant-time implementation ([#&#8203;153](marshallpierce/rust-base64#153), presumably `ConstantTimePortable`?) for security-sensitive applications that need side-channel resistance, and CPU-specific SIMD implementations for  more speed.
    -   Standard base64 per the RFC is available via `DEFAULT_ENGINE`. To use different alphabets or other settings (padding, etc), create your own engine instance.
-   `CharacterSet` is now `Alphabet` (per the RFC), and allows creating custom alphabets. The corresponding tables that were previously code-generated are now built dynamically.
-   Since there are already multiple breaking changes, various functions are renamed to be more consistent and discoverable.
-   MSRV is now 1.47.0 to allow various things to use `const fn`.
-   `DecoderReader` now owns its inner reader, and can expose it via `into_inner()`. For symmetry, `EncoderWriter` can do the same with its writer.
-   `encoded_len` is now public so you can size encode buffers precisely.

</details>

---

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Reviewed-on: https://codeberg.org/Calciumdibromid/CaBr2/pulls/1683
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crates/config/Cargo.toml

@@ -10,7 +10,7 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-base64 = "0.13.1"
+base64 = "0.20.0"
 directories-next = "2.0.0"
 lazy_static = "1.4.0"
 log = "0.4.17"