docs: Add initial benchmarks

docs/PERFORMANCE.md

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+# Benchmark Projects
+
+For all benchmarks below, execute `ui5lint` without any parameters. Benchmarks created based on [Benchmarking UI5 Tooling](https://sap.github.io/ui5-tooling/stable/pages/Benchmarking/):
+
+```sh
+hyperfine --warmup 1 \
+'node $(which ui5lint)' \
+--export-markdown ./bench.md
+```
+
+**TODO:** Memory benchmarking
+
+## Non-JS library, no findings: OpenUI5 `themelib_sap_horizon`
+
+_Reference commit: [`0efb2cd`](https://github.com/SAP/openui5/tree/0efb2cd89a893b499f40c43c7534240524c5de42/src/themelib_sap_horizon) (tag `1.120.10`)_
+
+**Metadata:**
+
+* Resources to lint: `0`
+* Result: `0 problems (0 errors, 0 warnings)`
+
+## Small app: `openui5-sample-app`
+
+_Reference commit: [`fa6d40d`](https://github.com/SAP/openui5-sample-app/tree/fa6d40d2a3ef7c7bb7c416117a0efc675ec90c65)_
+
+**Metadata:**
+
+* Resources to lint: `16`
+* Result: `6 problems (6 errors, 0 warnings)`
+
+## Medium library: OpenUI5 `sap.ui.layout`
+
+_Reference commit: [`0efb2cd`](https://github.com/SAP/openui5/tree/0efb2cd89a893b499f40c43c7534240524c5de42/src/sap.ui.layout) (tag `1.120.10`)_
+
+**Metadata:**
+
+* Resources to lint: `497`
+* Result: `1308 problems (1308 errors, 0 warnings)`
+
+## Large library: OpenUI5 `sap.m`
+
+_Reference commit: [`0efb2cd`](https://github.com/SAP/openui5/tree/0efb2cd89a893b499f40c43c7534240524c5de42/src/sap.m) (tag `1.120.10`)_
+
+**Metadata:**
+
+* Resources to lint: `4914`
+* Result: `11937 problems (11937 errors, 0 warnings)`
+* This is around 10x more than sap.ui.layout
+
+# Benchmark Runs
+
+## March 11, 2024
+
+* UI5 linter [`5466be5`](https://github.com/SAP/ui5-linter/commit/5466be5b983c4c6e6108c0d97d5221b8ad320a88)
+* Node.js `v20.11.1`
+* MacBook Pro M1 Max
+
+```mermaid
+---
+config:
+    xyChart:
+        xAxis:
+            labelPadding: 20
+        yAxis:
+            titlePadding: 20
+---
+xychart-beta
+    title "March 11, 2024"
+    x-axis "Project (number of files)" ["themelib_sap_horizon (0)", "openui5-sample-app (16)", "sap.ui.layout (497)", "sap.m (4914)"]
+    y-axis "Runtime (in milliseconds)" 
+    line [442.6, 2171, 6002, 34470]
+```
+
+### themelib_sap_horizon
+
+| Mean [ms] | Min [ms] | Max [ms] |
+|---:|---:|---:|
+| 442.6 ± 33.8 | 409.4 | 529.5 |
+
+### openui5-sample-app
+
+Mean [s] | Min [s] | Max [s] |
+|---:|---:|---:|
+2.171 ± 0.072 | 2.076 | 2.315 |
+
+### sap.ui.layout
+
+| Mean [s] | Min [s] | Max [s] |
+|---:|---:|---:|
+6.002 ± 0.064 | 5.936 | 6.127 |
+
+### sap.m
+
+| Mean [s] | Min [s] | Max [s] |
+|---:|---:|---:|
+| 34.470 ± 0.421 | 34.178 | 35.585 |